You need the six cylinder bell housing, they are different from the V8 units. The transmission is the same on the later H and M series six cylinders (you may hear different but only the G series had different transmission cases). The six bell should be dirt cheap, everyone seems to want the V8 just for the exhaust sound.
You should build a flathead Ford six powered jailbar tonner, you will enjoy it. Also,
I really like Ford six cylinders...