Hey stinky.
I've not done one of these jobs, but i envy you greatly. AFAIK, the gear ratio's are the same between the boxes, only difference is that the 5spd Dual Range box has the Dual Range and the 4wd selectors in the extension housing.
Now i'm sure you could with the 5spd AWD box and a 5spd Dual Range PT box create a dual range AWD box. Only problem would be locking the centre diff for 4wding, unless you could find a tight LSD to put in there like the EJ boxes. You'd use (in my mind) the bottom gear set (with the centre diff on it) to replace the one in the PT Dual Range casing, retaining the input shaft + top gearset from the PT Dual Range box. This should give you the Dual Range parts + the AWD parts. Use the AWD extension housing out the back, it will bolt straight on.
The other thing you'd have to do is make a stopper for the Low/High range selector arm so it will hold in either low or high with out you having to hold the gear stick all the time.
(I hate advertising my threads twice in one day but) check out this thread
showthread.php?t=4311
There'll be some pics in there that might help you out.
Cheers
