A rebuilder of the NP203 and 205 who is supposed to be the guru of these responded with this:

"you have a 203, great cases till they mess up. most parts still avaliable except chains.
you can put a part time kit in them 2 make 2 wheel drive.
if you go with a 205 like i have advertised you will have to have your tranny rebuilt with a longer output shaft"

So he rebuilds these by the dozens and doesn't know they don't have chains? And drivetrain.com indicates chains? What gives?

Stumpy, high mileage truck. Just like everything else, they can stretch, and break. It does happen.