Manifold ID in early A-Body
I have heard rumors that the exhaust manifolds from 318/360 Magnum pickup will work (in an early A-Body) with a little massaging. That would be a last-ditch alternative to tubing headers. Ask around; there might not be insurmountable obstacles in getting the Magnum manifolds on there. Word has it that the '92/'93 Dakota manifolds have bigger outlets than the later ones, but I'm not positive about that. I think the early ones are 2.25," if I remember correctly (and, I hardly ever do, anymore...)
Bill