Get rid of the fuelie or double hump heads and get some vortec heads...even fully ported fuelie heads won't hold their own agains a set of cheap stock vortec heads.
I just did one of these for a customer, he did put the GLM exhaust on the boat and he did have a set of AFR 195's on it. Let me find the e-mail with the power..Am I sure?
All of the research I have done and talking with others indicate the alpha will take 400 to 450.
I am trying to get ahold of merc engineering to confirm, but I am not of much significance when compaired to their normal work load, lol.
466#/ft @ 4400
433HP @ 5500
Torque was 423#/ft at 2900 rpm