You can gasket match the head ports but your heads are the same size as the exhaust manifolds before you touched them; if you look at your heads you can see what I'm talking about.
With that said I still gasket match manifolds being it doesn't take very long and smoothing out rough casting helps.
Where the up pipes bolt to you can remove a lot of material but you need to be careful b/c you can easily burn through where the bolt hole indent is. You'll want to get along bit and reach in there as far as you can so you remove the rough casting so you get smooth air flow.
If you want to make you're own set of up pipes Rick sells everything you need, bellows, bends, flanges, etc. But when you go to weld them you'll want to cap the ends & put a argon purge in there otherwise the stainless will "sugar" on the inside of your weld.
Cleaning up the manifolds is easy, just takes some time and patience. Making the up pipes take more time and patience though
. You need to make sure everything fits otherwise it can bind and blow a bellows. You'll also want to clamp it to a rigid bench so that when you start welding it doesn't stretch & shrink with the welding.
Yellowchevy
