Since I got the car and saw the 621 bell housing, I have been wondering if this was a late-year parts scramble or if someone had changed it over to a large clutch. Seeing the cast nose starter gave me further clarification and today my suspicions were confirmed when I pulled the bell housing to see what was in there. A jobber quality 11" clutch with a resurfaced 733 flywheel dated January of 70. I can only surmise the previous owner switched out the clutch when the motor was in and out of the car as it all looks like brand new with almost zero use.
In either case, it's coming off as I now look for another flywheel and a decent 10.5" clutch. At the same time, I'll install a correct 403 bell housing since I have another one sitting here that's ready to go. If only cars could tell the tale. Judging from the wear marks on the inside of the flywheel (block side against the crank flange) it looks to have been there for quite a while? Thoughts anyone?