I have a set of 561 casting LT1 heads that have been lightly ported. They should flow a lot better than stock. They were done at a local shop. At the same time he reconditioned all of the valves, installed new valve seals, checked the guides and gave them a 3 angle valve job. Heads only have 60K miles on them to begin with (came off a totaled 97 Z28). They will come with stock springs, retainers, and locks as well. Porter said they would be a great match for the CC503 or a similar cam. I have well over $700 invested in the porting and head work, not including the cost of the heads themselves. They are just in my way now that I have gone LSX. I can email some pics.

Asking $425 shipped in the lower 48

 

Do you have flow numbers for the heads?