[argonaut]

Its not just the available length. Both long bed and short bed pickups have the same length trailing arms. So best place to remove the 12" is from the section of frame in front of the center crossmember that the trailing arms mount to. Then just relocate the rear cab mounts and the front bed mounts 12" back. Otherwise if you cut behind the cab mount, you'll need to shift the crossmember 12" forward.

Unless it is a 4x4 or a GMC with rear leafs. Then you can cut right behind the rear cab mount.