LS-1 heads work good too. 17+ lbs of boost and 11's (and yea it is a 4.8)

 

i think i'll just wait till i have a bore to fit the heads.

 

the 317 heads and a good FI cam will work wonders with the radix on your 4.8.
the compression will be just right for a 93 oct tune at 13 to 15 psi.
that is almost at the point of doubling the horse power of that 4.8.
cold air intake, good FI cam, headers, tune, radix, 13 to 15 psi, and a set of 42 lbs injectors, should have you some where close to or over the 500 horse mark.
it would be a good idea to do the ARP bolt kit for the block and a Eaton for the rear end.
at that much horse power your 4L60e Trans will not last long.

 

Bore size is very important for valving. Its not really a matter of the valve size but how close the valves will be to the cylinder walls. Shrouding hurts velocity. Sure when you shove a blower on there it kinda evens things out. But ****, why do that? 4.8 has a small bore, using a head designed for a large bore. Jumping from a 1.89 to a 2" valve is a big step up.

 

If you think about it, a valve is only going to lift around 1/2". Most of the valve is about that much recessed into the chamber. If the valve were square, just for geometrical comparison, only one side would be affected by the extra shrouding. That leaves 3/4 of the valve to take advantage of the larger diameter hole. Not to mention the side that is being shrouded slightly more is also the side of the valve that is very shrouded by the combustion chamber as it is. I'd say the pluses and minuses would be a wash at best. It still might flow better with the 317's.

 

I did see Radix in there so all is good.