My 6.9 block is being bored 30 over with the rest of work. My biggest question is about 6.9 or 7.3 heads? I have a set of 1989 ,7.3 already rebuilt that I was going to use with ARP studs, however through (miscommunication or? ) I was given info on studs on ebay. These turned out to be 7/16 not 1/2 for 7.3 heads. So now will the 6.9 heads do as good of a job or should I get the correct studs and get the block drilled and tapped. I have to have the 6.9 heads rebuilt, so the cost of rebuilding heads or 1/2 studs and drill & tap are close. Also is the cost of coating pistons ($320 for top,sides and under) worth it? As always thanks for any input.