IMHO - If you are going to remove the separation in a dual plane manifold it defeats the whole point. In that case get a single plane manifold and lose low end torque for better high end hp. If this is as described - a performance street cruiser and you want low end response that you can feel when you punch it, don't screw around with you dual plane separation. The opposite would be true if you are going drag racing or concerned with top end Horsepower. The Stealth that I have has big ports, but I bought it used so it may have been tinkered with... Is there a 273/318 and 340/360 version of that manifold? Gasket matching on the manifold and heads is always a good thing like mentioned above, but better to have small ports into big than big ports into small so don't open the ports in the manifold way up and then have a lip where it hits the unmodified head ports.
