when I was entertaining a Dmax/Allison swap into a 71 K20, I found nothing on the shelf to hook up to an np205..
called several vendors, advanced, dirty laundry or something, diesel experts something, etc.. nothing allison to np205..
a saavy vendor down south recommended to look for later model mopar stuff, np 241 or something like that, also RH drop..
gal on the phone and her husband in the background spent at least 10 minutes giving me a laundry list of specifics..
still need adapters and speed sensor mod, etc.. couple of $k but at least doable..
I decided against it, not enough time for all of that, sounds like a good job for retired folks
here's the engine/trans I was looking at
07 LBZ Duramax 6 speed Allison
good luck!
eta: found my scratch paper..
Dave and K.C.
GM LAN
steering column shifter
tow/haul lockup
$2500 stand alone J1939
03-09 OE 4wd Allison tail housing, shaft, seal, bearing
Dodge motor mounts 89-93/95/98 lower profile
241 adapter $1300
OSS
shaft spline
RH drop early 90's Dodge 1500/2500 23 spline