American Racing Headers are the only full length long tube headers, all others are 3/4 length. With long tubes and a good tune you can average 15-20 HP across the RPM range on a basically stock car.
I have jba long tube headers jba off road x pipe ford racing stinger exhaust and blow by racing stage 1 cams all through an auto before lts and off road x with cats put down 330 hp to the wheels on the dyno sounds sick to
also I wouldn't go shorties unless you plan on getting a turbo I had shorties on mine before and hated them spend the money up front because it will cost ya more in the long run