I can't speak for the 3FE but can regarding a 1F to 2F. I originally thought that it would be a direct swap. Yes it's true that the motor mounts are the same, pattern wise, but it was still a lot of work regarding electrical, linkage, fuel delivery, etcetera. Sometimes I wonder if a 350 wouldn't be easier, certainly cheaper for maintenance/repair parts. I guess I'll find out on the next build!!!