The Fentons can be made to fit a gmc engine, but it takes a bit of grinding. The Fentons are actually made to fit the Chevy engines. There were other cast iron manifolds available for the 228-302 gmc motors but they are rather difficult to come by.
I will be using a set of Fentons on my 302 Jimmy. If I had it to do again, I would look for a set of headers that was specifically cast for the gmc engines.
