What are the casting numbers on the flywheels you have? I have a 14" (tooth to tooth) flywheel with casting number 3789733 I pulled off a big block motor about 20 years ago (it's dated August 12, 1968 if anybody is looking for one). The flywheel in my small block has casting number 3791021 on it. Unfortunately, I can't measure that one tooth to tooth for you as it's in the car. So I guess what I'm trying to say is, if your 13" flywheel has casting number 3791021 on it I would go with that one. Good luck.