I have the ET heads on a 512 ci. They have a couple of programs for those heads. At the time I got them I was 464 ci and they talked me into a standard port window. The 464 in my 3400lb with driver 71 dart went 10.0's. Ive since then built the 512 all the same stuff heads, cam, headers gears, ect. Best so far 9.88 @ 136. I sure wish I had max wedge runner now though