No acid experience here, but i did modify my 71 340 intake, milled the divider and blended the plenum area, tried best i could to radius the "90's " in the ports, gasket matched also, there was a lot of metal removed just from the gasket match. probably got 30 to 40 hours in the intake and about $20, looked into thermo coatings and was quoted $120 to do the bottom of the intake and the carb flange area but i passed. your best bet is to at least deep port gasket match it.