Re: 1978 Mercury Grand Marquis Specs
Hi, just joined the forum and saw your post. Did you find the info you were looking? Good sources for details are original sales brochures, dealer albums, parts books and service manuals. Most of these can be found on Ebay.
For a 1978 Mercury Grand Marquis with a 460 engine (engine code A) the transmission is a C-6 with a 9" rear end. The standard rear axle gear is 2.50The optional axle ratio was 2.75. If the Class III trailer towing package was ordered the rear axle ratio was 3.00.
I'm a collector of the 1977-1978 Mercury Grand Marquis's (have 16 in my collection).
Hope this helps