Planning to run AFR 195's, air gap, and roller cam. Prefer to run 91 straight fuel. I was hoping for 9.7 or so, but builder says I need to choose: 1)forged rotating assembly with flat tops/ 75cc heads = 10.1 or so 2)the same with dished/ 65cc closer to 9.2 or so He's suggesting option 2 due to having seen too many get ruined by feeding marginal fuel. He can get me to 9.7 (decking block, I assume) or so but will cost $$. He will measure prior to getting cam recommendation. He's been building engines for a very long time. A 2nd opinion I also trust says go with option one: "will run fine on premium, better MPG, performance". He's a hall of fame sprint car driver... He's why I'm spending a premium on heads. Just looking for strong, reliable street motor to mate with TKO600 and factory rear end. 430-450hp territory. I intended to avoid blended 93 altogether unless I go EFI, which sort of busts the budget. But I'll tolerate the wait getting her back on the road as long as she's set up just right and reliable. I've learned a lot here at nasty. Based on what I've read, I'm surprised he's that concerned about running low 10's with the aluminum heads. But she will run cooler in the mid to low 9's. The flat-top assembly is $200 less. leaning flat top but would appreciate any additional opinions on the matter.