I'm not against fixing any obvious port mismatch problems, or opening the manifold outlets as much as the pipes you're planning on using will accommodate.
But pumping abrasive slurry through exhaust manifolds doesn't seem to be a cost effective way to gain power in most of these applications.
I'd use that money somewhere that will make a difference...... Like a roller cam instead of a flat tappet.
Tony's 511 used aftermarket heads, and the port exits were likely larger than the OE manifolds, so making sure the manifolds were at least as big as the heads was a good move there(of course this assumes you can't bring yourself to running headers).
When I opened up the manifolds it seemed like where I needed to remove the most for aligning with the head's exhaust port window was where the manifold had the least amount of material, i.e. at the top. I removed some material from the top but was a little concerned at how thin it was getting. The good news is that the manifold's stud clearance holes are pretty big, so I installed the manifolds in the most up position and matched even with the head.Of course, this was with a ported aluminum head.
