Looking deeper into this ZF6 swap idea, I've come across a dilemma in the whole thing, specifically the 2003+ ZF6 and their 34 spline output shaft (or the 99-03 ZF6s with 31 spline).
Being that the 68RFE is a 29 spline output, the BW44-46 is expecting that obviously.
One option that comes to mind is swapping in a 29 spline output shaft from a GM ZF6.
The other option is trying to modify the BW44-46 to accept a 34 spline shaft.
Does anybody have experience with either of these options?