I pulled the Bellhousing off of a 1938 Dodge RC 218 engine, 25 inch block. The bellhousing is different on the transmission side They gave more room for the clutch plate. I Took some pictures , will try and post them later. You are probably right about the flywheels though too. The one that I had in the 36 I had replaced a while back. The one that came out of the truck was thicker on the block side . I'll have to measure them tomorrow. Anyway I should be ok now with the 218 bellhousing having more room inside at the top.
I did just realize though I would have to use a 37 or 38 transmission though because the 36 has the shifter moved forward. It sits on part of the bellhousing. I'm trying to find a different flywheel now.