I have a 1953 Willys CJ3A that needed a flathead four. The only engine I could find was the OHV four from a 1953 CJ3B. It bolted right up to the trans and the same mounts. The only difference was the OHV was taller than the flathead. The CJ3B had a hood that was 3 inches taller and my carburetor stuck up through a hole in the hood. If I put the air cleaner on I couldn't fold down the windshield. Other than the head it looks like the same block.
I test fitted a sbc in it but I would have to change the steering to do it. It bolted up to the Jeep trans and transfer case but I didn't think they could handle the torque.
I don't know if the jeep frame is the same as the 37 but they were based on the car so I think it's the same engine that they had in 37