If they have a 4 inch stroke and the single plane "hurt the bottom end power" they had something else wrong. Usually the wrong cam because we all love to buy off the shelf cams. Or the converter is way too tight. Or something else tune up wise.
Edit:BTW, the Pro Dominator is still the best TR you have in those pictures. Looks like a butt load of taper in that sheet metal manifold. You need taper, but if the outside is any indication of actual taper that's a lot.
