Hi Frank -
I don't know what the correct starter motor casting number is for your car. I would check with Ed. I bet he knows. I do know that the starter motors are date coded. The date code is stamped after the casting number and looks like this:
8 B 2 for February 2, 1968
Since you have a 11C car your date code should begin with a 7 and look something like this:
7 J 18 for October 18, 1967 (This is just an example. I'm not saying this should be your date.)
If you find out what the correct number is and the date code you want , let me know and I'll look for you next time I go to the salvage yards. Good luck.