I am sure they will fit fine. Here is a picture of some monster StageII heads on my production 4.1 block. (The picture was taken as a joke) They fit ok but why would you want to attempt it? You will not be taking advantage of the 14bolt configuration of the heads because the block only has 8. Also with heads that size and a large turbo, the stock crank would find its way to the pavement in short order. If someone was going to spend the money on StageII heads and intake I would hope the StageII block wouldn't be far away..
Then again I am always out to try something different so if you attempt it let us know what happens! powersix