I need to do something with my heads. There are 2 bolt holes in each end for mounting exhaust. Is one used for stock and if you go aftermarket you will use the other one? I assume the far end outside ones are factory mounting. What was the purpose for the one next to it and is this the one to use for Mac's or BBk? Did all 94Z's come with aluminum heads?

 

All years F and Y body LT1 cars came with aluminum heads. B-body cars had cast iron. You use the holes that line up with whatever you are installing.

 

Since the LT1 head is a traditional "D" port design the outside bolt holes are left from heads of the past. Any aftermarket exhaust manifold/header flange should bolt up to the stock location.