[Brad54]

If you've got a Dana 44 up front, just start looking for a used Jeep posi unit. Depending on what gear ratio you're running up front--Jeep guys swap posi units all the time. I bought one for my Suburban's rear axle for $100 off ebay (that was several years ago, but they're still there). They usually have 3-series gears, and are looking to go 4-series.
As long as you have manual hubs up front, and disengage them, it shouldn't make a difference whether it's open or limited slip. Once you're on the trail, on gravel, sand or dirt, it should handle just fine at speeds you'd be driving.

-Brad