We drew one up and had it made. Ended up being around $900 our cost not including labor to make. Sounds like similar design. We ended up not making a run of them due to being so expensive. We have a resplined 6l80 output, wiring harness and adapter for one of our builds ready to go in but for the other build we are running a 6L90 and pass drop np241 with factory large 29 spline. Have been running that setup for over a year now and love the improvement over the 4l60Not sure yet. Won't be ultra-cheap, but will do best I can and just a pinch over what is costs me to help out anybody else wanting such. 3/4" plate of 6061 aluminum, CNC work to have both flanges milled out, thick wall 5" OD 6061 aluminum joiner tube (this alone is $70 just for the piece), correct length hardened studs and flanged nyloc nuts for both sides, then the cost of having it professionally all TIG welded up once I index it. Right now I am determining its length, and then to re-spline the 6L80 short 4x4 output shaft, or buy and re-spline the longer 6L80 2WD shaft to keep good spline engagement and make the T-case adapter slightly longer at the same time to put it in the exact same spot. I think the front and rear driveshafts can probably handle some slight length difference, so TBD, I have some final measurements to do on trans vs trans length comparison, taking into consideration the length of the stock 4L60e t-case adapter, and to obtain the maximum amount of spline engagement possible for the 6L80 output shaft into the T-150 t-case.
This looks to be plug and play from the small amount of info out there on this (member 400ss on EFI Live forum did a good write up a while back). Company makes a CAN bus reverse light output relay, and can direct hardwire the tap up/down shift control if wanted.