Wecome to Outdoorking, Bobbybrian. The nearest item I can find in the parts and manuals section is a 12-38 illustrated parts list. The overhaul manual for all Briggs and Stratton engines made in that time period is here:
http://www.tpub.com/content/recoveryvehicles/TM-5-4240-501-14P/css/TM-5-4240-501-14P_70.htm
Just use the "next" button or type a higher number in place of the 70 in the URL at the top of your browser, to get other pages - there are 224 of them.

I haven't seen a workshop manual for your mower. If you care to post details of your problems here, with pictures, we may be able to help you solve them.