The problem is with the stock stroke and huge head chambers it's hard to get a decent compression ration with a flat top in a 383. If the shop just made the deck surface flat and installed the pistons, you need to see how far down in the bore they are. Most 383s have taller decks than blueprint and you'll want a static at least 10:1 with it. The best scenario is cutting the deck to get them .015 proud of the deck, then reduce the chambers as far as you can. I believe you can get them down to 68 ccs without any issue (.100") and that will get you a true 10.6:1 with a quench of .034". If you simply bolt on the parts and run the piostons on a factory-but-flat deck you will have a static ratio of 8.4 or so. Not nearly enough for that head as BJR suggests.