I think I'm going to take my broken diff housing to a local fab shop (only place I can think of with a TIG welder..) to do the same thing that Kreg has done... beefing up the ear.
Then when I mount it, I'm gonna be doing to strap of steel over the third-member, bolted to the cross member to eliminate twisting in reverse (which is how I broke my ear off). Hopefully my front housing will be much stronger than stock, and much cheaper than doing a GV swap.
As for the question of the GV front diff swap, You can't use the R&P gears, since as Rhinoman said, they are much higher than the Tracker. However, the housing itself will bolt right into your truck. (this is what I've come to assume, based on my research into the matter, although I can't confirm any of it).