Just FYI D2 and C8 both have the same exhaust port, matter of fact, they really are the same head, I think that even the harden seat benefit is a bit of a misnomer as they are induction hardened, and when ground bigger, it goes away.
They can support 500 hp, but it takes some work, as is 440-450 hp on a good day. FWIW I am having a set done for my 445 with a med riser port entry, aftermarket CJ sized valves and a lot of grinding, hoping to see 280 cfm, but that may be optimistic. Honestly, the C8/D2 heads are surely not heroes, but the truck guys don't have a lot of ptions
Regardless, C8/D2 heads are both probably the best bet for most trucks as the headers more readily match the low port "GT" heads. I actually mocked up my truck Hedmans on a set of Edelbrocks and couldn't get a port match and not have a header bolt jammed against a primary tube.