on a 91 GT convertible auto with 327 gears - “ IF “ I needed ( or wanted ,lol ) the top half engine rebuilt ( I know the term rebuilt is vague ) say a head gasket failed and needed to put a lot of labor hours in it . AND , I wanted to stay some what stock but get some extra HP power and torque from the effort . Does this sound like the way to go if head gasket change needed : retain the original iron heads ( more durable to resist warping ) have machine shop port them , change valves , guides , springs and add 1.7 rockers & port match the lower intake , then add some equal length shorties . Would this add some power ? Would stock throttle body , injectors and upper plenum be sufficient ?