I have the ex 262h with rhodes lifters installed in a 310 with the 416 heads and it sounds pretty healthy
I have not run it on the track or street yet,but I am sure it will do well!!!
I am sure it will make 275 -300 hp pretty easy.........
I have heard about alot of the stock gm heads for these engines being cracked too.........the aftermarkett would be the way to go,they probably flow alot better too.