The Berlina, Spider and Sprint were based on the corresponding models in the 2000 range, and all three inherited the body styling of their predecessors with minor facelifts.
 The biggest change was the engine.
 A brand new all-alloy 2.6 liter engine with six cylinders in line and twin overhead camshafts replaced the earlier four-cylinder engine with its cast-iron block and alloy head which dated back to the 1900 range of 1950.
 Two carburettors were fitted to the Berlina engines, giving 130 bhp (97 kW).
The Sprint and Spider engines had three twin-choke horizontal carburettors and developed 145 bhp (108 kW).
The OSI De Luxe was available with either the two-carb or the three-carb setup.
The Sprint Zagato had 165 bhp (123 kW) with the three-carb setup.

Total production for the Berlina was 2038 cars, the Sprint was 6999 cars, the Spider was 2255 cars, the 2600 De Luxe was 54 cars and the Sprint Zagato was 105 cars.

From a sales point of view, the 2600 models were not a success, despite deserved acclaim for their excellent engine.
The poor sales were not only due to the elevated prices of the 2600 models.
 The cars did not compare well with contemporary products, including those of Alfa Romeo itself.
 The factory had decided - correctly, as it turned out - to concentrate their limited development resources on the mid-sized Giulia which was introduced at about the same time.
 The flagship 2600 range was only a minor facelift of the 2000 range with a new engine, as this was all that the factory could do with the resources available.
 Since the 2000 itself had basically been a 1958 restyling of the 1950 1900, this left the 2600 with running gear a dozen years old at introduction.

The new engine also added weight and length at the front; though this did much for stability, it did not help the handling.
 Because the 2600 was a flagship Alfa Romeo model, expectations were high, and both critics and customers quickly spotted the deficiencies, both on paper and on the road.
 For example, the 165-400 radial tires fitted to the 2600 were a mere 10 mm (0.4 in) wider in section than the 155-15 tires fitted to the Giulietta, though the 2600 had considerably more power and weight.
 When the new Giulia appeared with completely new running gear, the 2600 was shown up even more.

Another reason for slow sales was styling and concept.
 The Berlina's styling was, to be polite, not happy and that reflected in the especially poor sales for this model.
While most Alfa Romeo sedans in the marque's history outsold the more specialised sporting models in the same range, the 2600 Berlina did not outsell the 2600 Sprint or Spider.
 The 2600 Spider had styling which was seen to be derivative of that of its smaller stablemate, the Giulietta Spider: certainly handsome, but lacking the smaller car's grace and balance.
 The larger car's handling also suffered perhaps unfair comparison with that of the Giulietta Spider, and this is an important factor in a car with sporting pretensions.
One sales point in its favor was that it was a four-seater convertible, though the two rear seats were fairly cramped.

The 2600 Sprint made more of an impression.
It was a large grand touring coupé which could seat four adults in comfort over long journeys at high speeds.
 As such, it did not suffer unfair comparisons with other models in the Alfa Romeo range as none of them could be directly compared with it.
 In that mode of operation, oriented more towards fast touring than sporting driving, the agility and handling balance of the smaller Alfas mattered less, while the stability and smoother ride of the larger car, and the wide power and torque band of the six-cylinder engine, came onto its own.
 Added to the greater space and comfort, those virtues made a convincing case for the 2600 Sprint.
The car also inherited the sharp, modern styling of its predecessor, the 2000 Sprint, and that certainly contributed to its being the top seller in the 2600 range.
That shape had been the result of Giorgetto Giugiaro's first major project as head designer for Carrozeria Bertone, and
The Berlina, Spider and Sprint were based on the corresponding models in the 2000 range, and all three inherited the body styling of their predecessors with minor facelifts.  The biggest change was the engine.  A brand new all-alloy 2.6 liter engine with six cylinders in line and twin overhead camshafts replaced the earlier four-cylinder engine with its cast-iron block and alloy head which dated back to the 1900 range of 1950.  Two carburettors were fitted to the Berlina engines, giving 130 bhp (97 kW). The Sprint and Spider engines had three twin-choke horizontal carburettors and developed 145 bhp (108 kW). The OSI De Luxe was available with either the two-carb or the three-carb setup. The Sprint Zagato had 165 bhp (123 kW) with the three-carb setup.
Total production for the Berlina was 2038 cars, the Sprint was 6999 cars, the Spider was 2255 cars, the 2600 De Luxe was 54 cars and the Sprint Zagato was 105 cars.
From a sales point of view, the 2600 models were not a success, despite deserved acclaim for their excellent engine. The poor sales were not only due to the elevated prices of the 2600 models.  The cars did not compare well with contemporary products, including those of Alfa Romeo itself.  The factory had decided - correctly, as it turned out - to concentrate their limited development resources on the mid-sized Giulia which was introduced at about the same time.  The flagship 2600 range was only a minor facelift of the 2000 range with a new engine, as this was all that the factory could do with the resources available.  Since the 2000 itself had basically been a 1958 restyling of the 1950 1900, this left the 2600 with running gear a dozen years old at introduction.
The new engine also added weight and length at the front; though this did much for stability, it did not help the handling.  Because the 2600 was a flagship Alfa Romeo model, expectations were high, and both critics and customers quickly spotted the deficiencies, both on paper and on the road.  For example, the 165-400 radial tires fitted to the 2600 were a mere 10 mm (0.4 in) wider in section than the 155-15 tires fitted to the Giulietta, though the 2600 had considerably more power and weight.  When the new Giulia appeared with completely new running gear, the 2600 was shown up even more.
Another reason for slow sales was styling and concept.  The Berlina's styling was, to be polite, not happy and that reflected in the especially poor sales for this model. While most Alfa Romeo sedans in the marque's history outsold the more specialised sporting models in the same range, the 2600 Berlina did not outsell the 2600 Sprint or Spider.  The 2600 Spider had styling which was seen to be derivative of that of its smaller stablemate, the Giulietta Spider: certainly handsome, but lacking the smaller car's grace and balance.  The larger car's handling also suffered perhaps unfair comparison with that of the Giulietta Spider, and this is an important factor in a car with sporting pretensions. One sales point in its favor was that it was a four-seater convertible, though the two rear seats were fairly cramped.
The 2600 Sprint made more of an impression. It was a large grand touring coupé which could seat four adults in comfort over long journeys at high speeds.  As such, it did not suffer unfair comparisons with other models in the Alfa Romeo range as none of them could be directly compared with it.  In that mode of operation, oriented more towards fast touring than sporting driving, the agility and handling balance of the smaller Alfas mattered less, while the stability and smoother ride of the larger car, and the wide power and torque band of the six-cylinder engine, came onto its own.  Added to the greater space and comfort, those virtues made a convincing case for the 2600 Sprint. The car also inherited the sharp, modern styling of its predecessor, the 2000 Sprint, and that certainly contributed to its being the top seller in the 2600 range. That shape had been the result of Giorgetto Giugiaro's first major project as head designer for Carrozeria Bertone, and 
Alfa Romeo 2600