Same for me. Chevy Duty did not stock the 9 bolt 10 3/4" pressure plate or disc for my 50 Chevy. I did send it to them and they rebuilt both and sent back in about 10 days. Try Keith Hardy's online Chevy Master Parts catalog for the original part no. It may help your parts man.
Here. Good luck. :p Be warned though; Keith has lots of great, useful info on the web (all free) but his server has lots of pop-ups!
