Shorties you do not gain much (alot of threads out there and alot of opinions on that topic) over stock manifolds if any. Long tubes will give you the most gain, with that said tough it depends on what your supporting mods are. If your just a basic bolt on car cold air intake and udp's then long tubes wont have the effect as if your were a ported na or Power Adder car. As far as bottoming out thats 100% dependant on the exhaust company, also the suspension on the car some guys here slam their cars and have real low stanc's others have more of a higher up or stock stance. Yes long tubes are expensive. If this as a 4v car (ie cobra mach one ect) and he put long tubes on his car you will gain considerably over stock manifolds (4v's love the LT's) but this being a gt, he needs to see what he wants. If its a DD stock manifolds or used shorties will work just fine. If you want Hp out of it, get long tubes.