The one thing I found on using them on my engine is there are actually 3 different ones for sbc. They normally list the ones for the 1957-74 as thin front seal, and the ones for 1986-97 as thick front seal. I have an early model block and a champ pan but the 57-74 gasket was to thin and the 86-97 was too thick. There is a medium one listed as being for 1975-85 part #OS34510T. Might be something to look into.
Curtis