Hey guys, I told you before that I found out that my 67' Biscayne appears to have a 307 in it (block casting number- 3970020). I found tonight that I appear to have some powerpack 283 heads on it as well lol. The numbers come as follow: 3884520 GM 4 T^-(big triangle lol) 0238-(may be 0288). These heads appear to be about 60cc chambers from what I gather online and 1.72/1.50 valves. Do you think these heads could support up to 300hp with a 1.94 intake valve? Anyone have any experience with these as I personally do not. Any help would be great!