My guess is the 3500 like the 4500 has the adapter built into the 4x4 tailhousing. Google seems to agree w/ me. There are aftermarket mounts for the 205. There are passenger drop NP241s out there that are a bit better than the 208.
One thing to be aware of is the round pattern on the 3500 may not quite line up with a 208/241. Not many of either were made for passenger drop and round pattern. The 205 will need an adaptor for sure unless you hunt down a round pattern one, which are also rare. Then there's the issue of spline count on the 3500; 27 is very light duty and 32 is less bad.
Pic of 4x4 3500:
https://www.google.com/search?q=4x4+...wugmFoWLZy9GM: