I've seen several of these conversions but as pre'68 Dave says, it's major work. The 250 uses same bellhousing as a V8 so you can get to a more modern standard trans like a T-5 or an automatic. Re. mounts you'll need to pick up aftermarket mount kit, believe Langdon't Stovebolt carries them. These are side mounts so you wont need the old front one.
Easy swap would be the 235, only a couple issues to overcome vs. several with the 250.
