I would use the floor and firewall from the 76...mate yours to it..I do believe the 69 or 70 Pontiac lemons is a much better fit frame for that conversion it's almost a perfect fit..if your using a GM drive train..Here is a link that have some food for thought..This a big job so plan well or you will be in deep and you need deep pockets..

http://www.jalopyjournal.com/forum/threads/50-merc-chassis-swap.694864/

Thanks fatchuk, like I said I have researched it and the Cougar has the same wheelbase side to side. I may have to play with rim backspace and tire width, but it is very close. when I get the Cougar body off I will post some pics, Thanks for your input!

the old G bodies - because you got new floor pan firewall, without touching the newer wiring, brakes and drivetrain etc
welding in the rockers and trunck was apparrently easier than having to swap in suspension , wirining brake booster etc etc etc etc

and wheel  base was within an inch, and track width was the same, and you could channel the car and and and and  - there were tons of reasons for doing it lol

AND - you could walk into any parts store to get parts anywhere you happened to be

-- Edited by Seeker1056 on Thursday 21st of January 2016 07:41:42 AM