The part no. is 16643 by Magnaflow Performance exaust.This part no is for 66-72 but my truck is a 65 GMC coil spring truck,and a long box.My truck has a 4" drop in the rear and I still have clearance. They recomend 1/2 " for clearance.The mufflers and tail pipe do sit up high in the box like stock. there is still travel room for the rear end , aprox 3 or 4 ". Something I dont worry about because I will never carry anything in the back anyways.
