trailing arm crossmember location

[Couch]

I posted this in suspension, got views, but couldn't get a response. just wanting a little reassurance.

I recently purchased a porterbuilt trailing arm crossmember and am planning on backhalfing my pickup with the chris alston battle cruiser kit but I will be remaining trailing arm. my question is, it is currently a 72 longbed frame- if I remove the factory TA crossmember and install the PB fab one a foot further towards the front, then lop off the frame behind it and weld in the back half, that will essentially leave me with a shortbed wheelbase correct? just want to be sure from all of the posts that ive read.