I put an electric fan on my '48 with a 235 in it, and I needed a thermostat housing that fit the motor but had a threaded hole that would fit the fan thermostatic switch. I went to NAPA, got out the picture book, looked for a housing that looked the same and then matched up the gaskets.
A thermo housing for a 350 for a van fit perfectly. I don't recall for sure, but I think it was a '78-80 G30 that fit the bill.
I'll bet you can find one that way, if you can't find another motor with one that fits.
