Ray
the coolest lens for the HCam is the Zeiss Planar 1,4/85mm. It covers full frame supersoft with a bit of vignetting wide open and perfectly sharp and covering from f8-11,5.
I also have an old vivitar 1,2/55mm which gives about 40x40mm wide open with a beautiful bokeeh. About the same for the 1,4/50mm zeiss planar, Most surprising my recent discovery: the old AF-D Micro Nikkor 2,8/60mm covers full frame 645 razorsharp ! Same with the Zeiss 2.0/100mm Makro.
there are so many lenses to try : best candidates old Contax and Leica R. I had a Leica 2,8 180mm covering 645 not quite but with nice bokeeh. a 250 telyt was perfect.
The longer teles may work depending how far their back lens is inside the barrel. real teles longer than 300mm may cause barrel vignetting, long telezooms will probably work most.
Greetings from Munich
Stefan