[Mike C]

Those are for an LS as mentioned above, won't work with a big block. As I mentioned above, the big block Corvette reproductions are the best value in a better flowing big block manifold. The other option is the original style manifolds on the truck, a set from a Vortec vintage 7.4L or a set of Sandersons. The Sandersons use a collector style gasket to the pipe so are not quite as leak resistant as other options. And they are stupid expensive at $700. I have a set I will run if the 'vette manifolds are a bust.