Frame swap

[willie 64]

picked up a 1964 c-20 pick up with a 230 6 cyl 3 spd .i want to lower the suspension i read on this site about the dropmember and z-ing the frame. then my brother gave me a 1988 c-1500 pick up in rough shape .i pulled the cab and bed off and i am going to use the chassis from the 1988. i am going to channel the cab because the floor and cab mounts are rusted out.the front i guess dropped spindles and air bags will get it down. what could i replace the leafs in the rear ? here are some pictures of the truck and current project.