That isn't the problem. The problem is that the extended flat surface below the exhaust ports prevents the early A body exhaust manifold from laying flat against the head. Grinding for clearance results in cutting through into the water jacket.
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I've done what you suggest though.
There are some later 318/360 manifolds that do fit but the steering coupler is in the way. The fix for that is a smaller Borgeson U-joint coupler. It isn't a perfect fix though....You lose the "plunge" feature that the stock coupler has.
