My '67 std is due for new exhaust. Car is equipped with a 289 4V w/mild cam & C-4 trans. The headers on the car are well past their prime (numerous leaks) and the glasspack mufflers are about to fall from their rusted exhaust moorings (the whole system was put on the car about 25 years ago). I love the sound of the glasspacks and will likely just replace them. Should I stick with a standard length header or would shorty headers be a better option? Would this make any difference at all?