Re: GT40P Heads
the heads burn cleaner, with better mileage and more power compared to standard gt40 iron heads, wich were better than the stock heads on your motor. the major reason for this all around better head is the relocated spark plug..moving the spark plug allows combustion chamber geometry revisions as well as the inherent benefits of an optimally located spark plug....the problem is that with the revised spark plug position comes header and manifold clearance issues. The bolt pattern is the same, but plugs may be hard to get at, depending on which headers you use, you may need: funky u-joints, flexy ratchets, clearance denting your primary tubes on some cylinders, using shorty plugs, and 90 degree boots with heat shielding....if you run platinum plugs (to avoid the hassle of changing them often) and are patient routing the plug wires you should be o.k....i know there's a gt40p website out there with a little bit on a 5.0 bronco motor w/ these heads..
oh! btw, the heads have 7/16" headbolt holes, so they bolt onto 302's w/o steped head bolts, but you'll have to have them drilled to 1/2" if you want to use them on a 351
i think they're worth about 40hp