Asked in Pontiac Grand Prix
Will a 1968 Pontiac motor fit in a 1978 Pontiac grand prix?
It should fit fine. The 455 will be tight fit with ac. I have a 71 Pontiac 350 Catalina engine in a 80 Pontiac grand prix with everything hooked up except smog pump. Lots of room left.
Yes it will fit, There were no 455s produced in 1968. The largest Pontiac V8 that year was the 428. 455,428,421,400,389,370,347,326,317,287 and 350 Pontiac motors are all physically about the same external dimensions. The is no "small" or "big" block Pontiac V8 except for the 1977-1981 265/301 which were the same legnth as earlier V8s, but had a 1" shorter deck height. The only potential problems you may have are changing motor mounts (pre 1970 blocks only have 2 mount bolts per side), wiring issues (starter on wrong side if a Chevy originally), and if the car was originally equipped with a Chevy engine the transmission will not bolt up, as Buick,olds,Pontiac use the same bellhousing, Chevy has a different pattern.