Hi, years ago I put a 428 Ford big block with C-6 transmission in a 47 (same frame and size as yours). I really did not have any major problems with the install so SBC being so much smaller in every dimension and lighter, it should be a snap. Simple to make you own motor mounts and transmission mounts.

In the light of "To each his own" if I were building a new 41, I would chose a 98 Lincolin Mark VIII 32 V V-8 with its transmission. Sweet ride with lots of power and easy to get more power. But you are not building that car for me or anyone else here who gives you advice, so have fun picking out what you want.