Can't believe finding a clutch would be a big deal, there are still a lot of the 40s Mopars out there that most likely used the same clutch.
Check www.robertsmotorparts.com and might be worth checking your local NAPA store. In a worst case deal, you can probably get your clutch relined.

Personally, I'd get it running and see if there really is a problem. Maybe its just out of adjustment? Gene