I have a very old speed, I bought it in 1966, used Navy surplus, if I had known it would be money would have taken better care of it. Over years the I dropped it and broke the rangefinder, held together by duct tape, like you I used as a field camera, also have a 6X9 Graphic, I don't think it ever had a rangefinder, no focal plan shutter, on my list to find a 100 or 101 Houseman super that will cover more movement than the Kodak on the Bush. Not sure about a Mamiya TLR, but the 150 and 250 from the press line up should work, the 150 is pretty light the 250 is a heavy large lens. How bright is the viewfinder on your Graphic, the Bush is really pretty dim.