I have made a bunch(ten or more) of stock stroke pump gas 440 motors that made 500+ HP with more torque than HP. None of them where what I would consider a "quench" motor, all of them had flat top pistons, some with valve reliefs some not. Most of the iron heads had the same size valves as yours but some where stock size with mild porting, the best heads flowed 266 @ .500 on a Super flow 600 bench using 28 inches of water on the intake side. The cams varied from a Comp Cams XE28HL to a solid lifter Reed cam(the most HP ,535 HPat 5900 RPM,and Tque 560 FT lbs at 4200 RPM )that was ground on a 101 LSA Take a good hard look at Comps XE-HL sereis hydraulic cams Most of those motors had either a Eddey Performer RPM intake or a Mopar single plane 4150 with at least a 800 CFM Holley or BG double pumper, three had the Holley 950HP. Your set up and car combination would make me want to use the Comp Cams XE284HL with a set of 1.6 rockers and a good 3000 RPM converter (11 inch )