I'll add, unless the motor's putting out more than 280-290HP, replacing the stock HO shorties with aftermarket shorties won't help a thing. Despite their appearance, they don't inhibit peak power til you get up close to 300HP. Now, a set of long tubes will help bottom end, but if you can't do the rest of the exhaust, you can't build custom long tubes; and having someone else do them would be very expensive.