On my sticker there is no difference for manual trans with or without A/C. The only difference for auto trans cars is a slight increase in idle speed. I also looked up the the specs for the amount of vacum and mechinical advance for 1978 nova and camaro. Both cars use the same part number and advance curves for auto OR manual trans. In other words you could run 10 degrees of of advance to start and if it doesn't ping it would be no difference in total advance from an automatic trans car.(a very tame curve IMHO)
