If the rear end doesn't look like one of ours then someone put a different rear end in that truck. The only difference between mine and redheadhunter is that mine has blocks under the leaf springs because mine is a 4x4.
posi or no posi, it uses the same axle. It's called limited slip on a dodge also.
The tow package is just the hitch and trailer wiring, nothing to do with the rear suspension.

 

I have the LSD and the tow package and there shouldnt be much of a difference if any is your spare under your truck might look different because of that