Here is my question can you use either 10.5 or 11 inch clutches with the same flywheel and bell housing? Will they both bolt on to the same flywheel? If not is there a way to tell which one I have in my 70 highboy without taking it out and measuring it?

 

If it's a big block, it is most likely 11", even the 302 in a truck back then had an 11".

Can't speak for certain, but likely a stock flywheel will not have dual patterns. The 184 tooth flywheel was 11" clutch. The 157 tooth was 10 1/2" clutch.

 

Going from memory 300,302,360 all had 11". 390 had 12". If I am wrong NumberDummy will chime in when he catches this thread.

 

most newer flywheels are double drilled for 11 or the 11.5 clucth. 390 truck 11.5 that i've come across. Way back in the early 60's had car with a 1962 HP-390with a 12" clutch tho.... orich