If you're looking for a 645 with the feel of 35mm, look at a pentax 645 n2. I would suggest also considering some medium format RFs- there are a number of fixed-lens Fuji 645 RFs that perform very well and are comparable in feel to 35mm. Also consider a mamiya 6/6mf/7/7ii, the 6 is my favorite camera overall, no question. It really evokes 35mm in term of handling.
As a former mamiya 645AFD and current mamiya 645 pro owner, I prefer the modularity of the latter. There are many fantastic lenses too. But it annoys me somewhat that the pro is almost impossible to work with in portrait orientation, without the finder and grip. And although it is a very sweet little bundle without the grip and finder, I would not compare it to a 35mm camera. I did treat the 645 AFD a lot like a 35mm system, and did sports and low light stuff with reasonable success. I just didn't care for the AF system and couldn't justify carrying the body around with me when I was almost always focusing manually. The newer AFDs should have much improved AF, if that matters to you.
Anyway, the best thing about the mamiyas is the lens availability- you can't go wrong there. Huge selection- old and new.