I'm putting a 454 in a70 Chevelle that was initially a 350. The frame mounts appear to be spaced wider that the mating engine mounts. Is there a difference between big block and small block frame/motor mounts?

My Assembly Manual for 72 Chevelles....same frame/same body....shows the same part numbers for big and small block frame mounts, engine mounts, and they all bolt in the same holes.....and yes it does work. Your big block will bolt in the same location using the existing mounts. Do be sure you have the correct oil pan, otherwise the motor will not go in.

Shannon

The frame and engine mounts are identical between a 350 and 454.

little additional tip having done this swap. if you put a big block into and previous smallblock car you have to bolt on the small block mounts to the big block otherwise you will be 1/2 too high up on the perches.