The adaptor would have to be sticking out from the front to have enough room for coolant to get into the block, this would put the water pump even farther forward creating a whole other problem. A 250 in a '37 is tight as it is, moving the pump will make it worse. It's not ideal, but an electric cooling fan solves a lot of issues with radiator location.
My radiator is as far forward as it can be, I cut part of the chin sheet metal away and removed the cross bar in front of the radiator just to gain more room. The 17" fan still goes below the core and filling it with coolant takes a 6" hose on a funnel to reach the opening.
A jack shaft won't work, the thermostat is just above the pump, so you would need even more cobbled up parts to make it work.
