Ellis Vener has made a few good posts on photo.net about the Hasselblad H1, which he's been using for a while. You might do a search over there and see what turns up or dig up his e-mail and contact him directly. If I were in your situation, this is probably the first camera I'd look at.
Have you tried a focusing screen upgrade for your current system? Sometimes a brighter screen and focusing aids like a split-image circle can make a big difference.