The 5R has many clutch disc or plate as they were fitted to different transmission such as the M40 and M50, although the R40 that the stouts had pre 1979 has a smaller input shaft which limits the things slightly, I do not doubt there is a clutch disc/plate with the overall diameter and input spline count and shaft size as here in Australia there are a couple of companies that make adapters to fit various engines to the stouts original R40 transmission including ford chev and Chrysler V8's on off the shelf replacement parts.