Thanks, Dave. I did get a number from that lip area, I think it is the engine id code, not the casting number. I found this page: http://www.nastyz28.com/spmenu.html so my ID code is V0524TJZ, which means Flint, May 24, 1973 truck engine, but I still don't know if it's 2 or 4 bolt mains. The heads are 1972 3998933, very common 76cc heads from what I read. Any other place I should look for the actual casting number?