as i said before im no mechanic, the pistons are flat top with 4 valve reliefs in them,is that considered stock? also the guy that i bought the motor from said he built it for towing, the block has been decked a little bit,i dont know how much. he also told me it was bored .030 over . i didnt know matching the pistons was so critical. im starting to get the feeling i should have bought a GM performance engine instead of going this route. does any of that stuff make a difference?