74 to 64. ???

As GGs66GT said, the whole drivetrain will fit if you want to use an aftermarket shifter or install a '66 A-body automatic column and linkage setup. You may have to get a different length driveshaft and you'll have to swap over the engine oil pan and pickup from the '64 engine. There will be other items that will need to be swap over too....like the carb, dist, and engine mounts, but those are easy.