Originally Posted by A_VAS
you can use a LS7 head yes, if you drop down to smaller exhaust valve size.
I wouldn't even try dealing with the hassle of trying to get a smaller exhaust valve in an LS7 head. Changing to a smaller valve would work but it would more than likely mess with the efficiency of the head. It wouldn't release the full potential of a motor of the size of the OP.
Originally Posted by N2OBaby
Hot Rod mag built a resleaved LS3 block to 468 cid and they got good results from LS3 & aftermarket LS3 heads this maybe an option.
I wouldn't consider an LS3 head for a motor that size. My friend has a full weight GTO that comes in at 3800lbs he has an LSX block 451 in it that had LS3 ported heads on it. It ran 10.80's on motor he pulled them off and ran a set of LS7's on it and gained 3 tenths just from the head swap. The cam is a mild 23x/24x duration cam.
Will it work and make power? Yes.
Can it be better with a set of LS7 heads? Yes.
To the OP Texas-Speed also makes a set of small bore LS7 heads for applications just like yours. It is designed for 4.060 bore and larger.
Here is the link to them on TSP website. http://texas-speed.com/p-1236-prc-ls...cnc-heads.aspx
Here is a thread with alot of pics on it. TSP / PRC 265cc LS7 Heads for min 4.060 bore