Looking at a set of Lt1 Heads, there is no way to get to the water jacket from the intake face. If you were to drill through the intake face and the intake face on the head you will not reach the water jacket in the heads. There is a 2" gap from the Intake face on the head to the water jacket. Looks like you could use the factory coolant crossover holes that are at each corner of the heads. Someone suggested to enlarge them ......1/2" pipe would work well but drill them offset of the stock hole instead of just enlarging the stock hole. I say this because it looks like the coolant would have a smoother path into the head. You may have to enlarge the block drain holes also..... I think they are 3/8" pipe, not sure if thats enough flow to get the coolant out? The engine masters big block uses the drain holes for the return but I cannot tell what size the block holes are. He looks to be using -8 or -10 hose.
If the AFR's coolant passages are different than Factory LT1's .....please ignore the above paragraph.

 

So... who do I send my heads to in order to have them converted?

 

You've got mail Jimbo.

-Mindgame