On a 5.0 fuel injected engine, smoothing the runners will not cause fuel puddling because the fuel is not injected until right before the cylinder head. On carburated engines, a polished runner would cause this condition. You are correct about not polishing the heads because they move wet flow (both fuel and air) rather than just air. I think that you would gain a few HP by smoothing the runners.
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67 Fastback - Arctic White Pearl paint
351W 415 hp, Trick Flow Alum. Heads, C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars.
