Need some help on truck specs

[Twiztid 83]

Hey all, been a while since I logged in here.
But I'm looking for specs (of all kinds, engine, trans ect ect...) on my
1983 Custom Deluxe, its got a straight six in it, and I'm wanting to find out
what the CI is on it. It also has a 3 speed manual, it was at one point a 3
on the tree shifter, but some one converted it into a floor shifter (which I
don't mind)

Also, the rear transfer case is making a bit of a "knocking" sound when
coasting at 5mph and under, anything above that and there's no sound.
Any ideas?

And the attached pics are renders of said truck.