Handbuild production, updates, and repairs throughout each car's competition history result in differences both visible and invisible between individual 250 GTOs.
 Variance in air intake/vent configuration is common among cars.
Modifications to the original bodywork were performed by the factory, Scaglietti, or other body shops, usually after crashes or according to a racing team's wishes.

In 1964, Ferrari tasked Mauro Forghieri and Mike Parkes with redesigning the 250 GTO's bodywork, resulting in what became known as the GTO '64 (or Series II).
Three new cars were produced to the 1964 specification, and four earlier 250 GTOs were retrofitted to it by the factory.
 This redesign was intended to maintain the GTO's competitiveness for one more year, as the FIA decided to not approve the 250 LM for GT-class racing during the 1964 season.
The Ferrari engineers incorporated many of the 250LM's aerodynamic features into the 1964 GTO.
This resulted in a visual similarity between the two models, even though the GTO does not share the 250LM's mid engine rear wheel drive layout.
The factory also made minor modifications to the engine, gearbox, chassis, suspension and interior.
Despite these changes, the overall performance improvement was slight.
The GTO '64 still saw some racing success with factory and privateer teams, including an overall win at Daytona in 1964 by Phil Hill and Pedro Rodriguez driving for NART.

Three 330 GTO specials were made using the 250 GTO chassis and body fitted with 400 Superamerica 4.0L motors.
Distinguished by a larger bonnet bulge, these cars were used briefly for racing and testing by Scuderia Ferrari before being sold to private customers.

The 330 LMB is sometimes considered a GTO variant.
These cars used a 4.0L 330 motor and a modified 250 GT Lusso chassis/body.
Four were produced in 1963.

Three 275 GTB/C Speciales were built in 1964/65.
Despite their origins as competition versions of the 275 GTB, they are sometimes considered developments of the 250 GTO due to similarity of configuration and bodywork.

The Ferrari 250 GT SWB Breadvan was a one-off racing car designed for Scuderia Serenissima by Bizzarrini after his departure from Ferrari.
It was developed specifically to compete against the then-new 250 GTO.
Although based on the earlier 250 GT SWB, the Breadvan provided an opportunity for Bizzarrini to develop the ideas he had first explored with the GTO, such as lower and more aerodynamic bodywork, incorporation of a dry sump, and radical lightening of the entire car.
Handbuild production, updates, and repairs throughout each car's competition history result in differences both visible and invisible between individual 250 GTOs.  Variance in air intake/vent configuration is common among cars. Modifications to the original bodywork were performed by the factory, Scaglietti, or other body shops, usually after crashes or according to a racing team's wishes.
In 1964, Ferrari tasked Mauro Forghieri and Mike Parkes with redesigning the 250 GTO's bodywork, resulting in what became known as the GTO '64 (or Series II). Three new cars were produced to the 1964 specification, and four earlier 250 GTOs were retrofitted to it by the factory.  This redesign was intended to maintain the GTO's competitiveness for one more year, as the FIA decided to not approve the 250 LM for GT-class racing during the 1964 season. The Ferrari engineers incorporated many of the 250LM's aerodynamic features into the 1964 GTO. This resulted in a visual similarity between the two models, even though the GTO does not share the 250LM's mid engine rear wheel drive layout. The factory also made minor modifications to the engine, gearbox, chassis, suspension and interior. Despite these changes, the overall performance improvement was slight. The GTO '64 still saw some racing success with factory and privateer teams, including an overall win at Daytona in 1964 by Phil Hill and Pedro Rodriguez driving for NART. 
Three 330 GTO specials were made using the 250 GTO chassis and body fitted with 400 Superamerica 4.0L motors. Distinguished by a larger bonnet bulge, these cars were used briefly for racing and testing by Scuderia Ferrari before being sold to private customers.
The 330 LMB is sometimes considered a GTO variant. These cars used a 4.0L 330 motor and a modified 250 GT Lusso chassis/body. Four were produced in 1963.
Three 275 GTB/C Speciales were built in 1964/65. Despite their origins as competition versions of the 275 GTB, they are sometimes considered developments of the 250 GTO due to similarity of configuration and bodywork.
The Ferrari 250 GT SWB Breadvan was a one-off racing car designed for Scuderia Serenissima by Bizzarrini after his departure from Ferrari. It was developed specifically to compete against the then-new 250 GTO. Although based on the earlier 250 GT SWB, the Breadvan provided an opportunity for Bizzarrini to develop the ideas he had first explored with the GTO, such as lower and more aerodynamic bodywork, incorporation of a dry sump, and radical lightening of the entire car.
Ferrari 250 GTO