In conjunction with the downsizing of the model line, the third-generation Marquis and the adoption of the Panther chassis transitioned towards increased parts commonality between Ford and Lincoln-Mercury full-size lines.
 Along with a common wheelbase (for the first time), the Marquis and the Ford LTD shared nearly their entire bodyshell; many non-visible components were shared with the Lincoln Continental/Town Car and Continental Mark VI.
 Distinguished primarily by trim, the LTD and Marquis shared a common roofline (the Marquis 4-door is distinguished by a full-length vinyl roof).
  The two-door hardtop and four-door pillared hardtop were replaced by sedans with fully framed door glass with fixed quarter glass in the rear side doors (each model had its own door design).

While both model lines shared a common bodyshell, several detail changes were made by stylists to distinguish Ford and Mercury full-size sedans from one another.
 While the LTD received an egg-crate grille design, the Marquis was given a vertically-oriented grille (similar to the 1978 Marquis and the 1980 Cougar XR7) and parking lamps similar to the 1975-1978 Marquis; hidden headlamps were abandoned.
 In line with the previous generation, the Marquis received full-width taillamps (bordering the license plate).
 In a feature adopted from the Mark series, the Marquis was styled with (non-functional) fender louvers behind the front wheels (and vents in the front bumper).
 Ford, Lincoln, and Mercury each received its own dashboard design; Mercury received an instrument panel with square white-face instrument bezels.
  In 1982, the Marquis introduced a digital trip computer (an option, replacing the analog clock in the dashboard).

During its production, the third-generation Marquis saw few major revisions.
For 1981, the air vents were removed from the front bumper (and from the fenders in 1982).
In conjunction with the downsizing of the model line, the third-generation Marquis and the adoption of the Panther chassis transitioned towards increased parts commonality between Ford and Lincoln-Mercury full-size lines.  Along with a common wheelbase (for the first time), the Marquis and the Ford LTD shared nearly their entire bodyshell; many non-visible components were shared with the Lincoln Continental/Town Car and Continental Mark VI.  Distinguished primarily by trim, the LTD and Marquis shared a common roofline (the Marquis 4-door is distinguished by a full-length vinyl roof).   The two-door hardtop and four-door pillared hardtop were replaced by sedans with fully framed door glass with fixed quarter glass in the rear side doors (each model had its own door design).
While both model lines shared a common bodyshell, several detail changes were made by stylists to distinguish Ford and Mercury full-size sedans from one another.  While the LTD received an egg-crate grille design, the Marquis was given a vertically-oriented grille (similar to the 1978 Marquis and the 1980 Cougar XR7) and parking lamps similar to the 1975-1978 Marquis; hidden headlamps were abandoned.  In line with the previous generation, the Marquis received full-width taillamps (bordering the license plate).  In a feature adopted from the Mark series, the Marquis was styled with (non-functional) fender louvers behind the front wheels (and vents in the front bumper).  Ford, Lincoln, and Mercury each received its own dashboard design; Mercury received an instrument panel with square white-face instrument bezels.   In 1982, the Marquis introduced a digital trip computer (an option, replacing the analog clock in the dashboard).
During its production, the third-generation Marquis saw few major revisions. For 1981, the air vents were removed from the front bumper (and from the fenders in 1982).
Mercury Marquis