Yes i know i have to bore it . Im about 2 send my block 2 a machine shop but i havn't decided what pistons 2 use or if i want keep the stock ones . I just heard that if I use gsr pistons I have to modify the pistons and rods. Has anybody used ITR pistons on a ls bock if so ,what do I have 2 do 2 slap those babys on.