The main difference between the manual-shift and electric shift B-W 13-56 is where the shift selector is located on the outer case. While the housing is magnesium and very similar on both, the electric shift motor is on the opposite side of the manual shift linkage. The internal parts are identical.
I agree that the best way to convert from electric to manual is to swap the whole transfer case, but you could just get a manual-shift case-housing and put your electric-shift "guts" in it.
The B-W 13-56 does have a better low-range ratio (2.72:1) than the NP205 (1.69:1), and weighs alot less (74 lbs.) The one problem I see with it is the mounting of the oil pump into a groove in the hosuing. There is a tech article on this, and how to fix it. Basically where the pump mounts to the case will wear out about 100K miles, and it could come loose. As long as the fluid level is kept full, the pump shouldn't fail.
For your swap, you will need the shift linkage from the B-W 13-56 that mounts to your type of tranny (E4OD), as they are specific. I would look for one as new as you can find, so it doesn't have alot of miles on it, but it's a good idea to disassemble and inspect a used one. Local junkyards want $350-$400 for a 92-96 model t-case.
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