I use custom-made helicoid adapter on my Sony for any projection lens I have (around 20 in total). There is pentax 645 to m65 helicoid-adapter available so it's not a problem to adapt any projection lens.
Mostly it's very fast lens, 90 1.25, 100 1.4, 141 1.9. So I wonder if it's possible to shoot with non-generic lens. I have 2 ways now: wait for new Sony a7iii or get used 645D without live view.
Also I want to ask about flange focal distance. For Sony most of my fast projection lenses have infinity working from around 30-40mm. That means I will not receive infinity or full body portrait on 645D using most of my projection lenses?