Hmm, since there is no sure way to tell from the casting numbers if it is a 4 bolt block or not, I'll just have to rip off the pan to find out. Thanks for the help, I did get the casting number off the block which was 361959, just a 73-85 casting, same with the 113 cc smogger heads. The engine has no EGR and its carbureted at the moment. I had heard it mentioned before on other sites, just couldn't remember where. I know what Hi-perf means....just not what it meant on this block; mains, steel crank, good rods, etc.