Hi jkcondrey. Yes I followed several and made some comments about my planning for this project(s) on a couple threads. I'm making a trailer from the cargo bed, so have post on what I did to my trailer also.
Post up a ink to your crew cab build, if you have one. That is a big change to make + 4x4.
I concluded I wanted full frame length and went back and forth on the bed, coming back to the M105 for a 4x4. What I build in the space from the cab back to the bed can be (length) adjusted.
Decision now is fitting the 105 bed, which I don't have yet, exactly in the right position that matches my; 1 frame and; 2 tail gate when lowered vs. pintle hitch and; 3 axle is centered on the wheel well.
My M105 drawing shows an inside length of 110". I need to confirm every inside and outside dimension to make the location. I want the rear gate to go down, fully vertical and just touch the pintle. Hopefully someone with M105 detail pictures will post up a few and take a few measurements. I specifically need a profile where the gate is fully down.
Since my pintle is fixed, the back of the bed has to be even with the end of the pintle. That then determines where the wheel well is located and thus the center of the axle and placement of spring mounts.