I tried the search, but couldn't find anything. Don't ask why, the 383 was cheap and I need to get the car moving under it's own power soon.

What changes would need to be done to make this work, as far as motor mounts, bellhousing, etc? Intake, distributor, bracets, etc, don't really care about, I've got spares of them or could get them easy enough. My concern is that it's not a pull one out, drop in the other, but I haven't found anything saying it's not yet. Thanks ahead of time for any help you can give.

same bell/mtr mounts. diff front mounts for alt/ps/ac etc as each deck is 3/4" taller than the "B" so the "V" is 3/4" taller if that helps visualize the difference. Ex pipes MAY be different. intake/valley pan metal gasket/ 2 valley pan end holdown flat plates/pushrods/dist/ are different.

The engines both utilize the same bellhousing pattern. Unless the RB was externally balanced, the converter should be neutral. If you had a cast crank 400 or 440, you could just remove any balancing weight from the converter to achieve neutral balance.
If the 383 is complete, most everything external as far as accessories bolt up as before. Exhaust sits a bit lower due to the B engine lower deck height. Throttle linkage, trans linkage...all fits pretty much the same.

Wow, thanks. This looks like it may be easier than I thought.