i am having a problem with my flex plate it will not slide into the transmission because it`s to big?? i am working on a 75 mustang with a 351w and either i have a c4 or c6 transmission not sure how to tell? i need to know where i can find a smaller flex plate to fit the 351w and the c4 or c6 trans. can anyone help me?? is there differant sizes?

 

the flex plates are different between the c4 and c6, not sure how to tell the difference visually between the transmissions hope this helps