There is a difference and I'm not sure what year the change was made. I'm guessing that it was 68, when they switched from the SM420 to SM465, and also changed the input retainer hole size. I had my 292 drilled and tapped for the 3 bolt starters that mount to the block. When I tried to put a 72 starter in it wouldn't fit. I ended up using the original starter. I'd suggest you find a shop that rebuilds starters, they will have the answer.
There may also be a difference in the number of teeth on the flywheel.
Larry
Last edited by LGriffin; 02/18/2009 2:36 AM.
