help please i have a 54 chevy 1.5 ton truck and my wheelbase is 137' i just picked up a nice set of bedsides from a 53 and they measure 7.5 feet from edge to edge but when i put them up on the frame there too short . im not worried about the rear of the frame. that can be shortened but when i have the sides close to the cab about a inch or two my rear spring shackle is almost to the end of the bed side . i can take them to my body guy and get them lengthened a little but i was wondering if im just missing something

thanks