[ed cougar]

You can have them extruded if you have the $$ not sure how much it cost nor where to have it done only heard about it from shop talk. For what it's worth they have an extrusion process whitch pumps a heavy grit claylike substance through the manifold under hydraulic pressure whitch removes material as it smooths the insides to a polished finish, maybe someone more knowledgable on the process can elaborate. I used a dremmel on my cj manifolds and tried to smooth them up inside but I grew impatient and gave up on it.