the truck should roll freely with the radio on and trigger in the middle. if the brakes are applied in neutral it could be causing drag under throttle. i would reset your throttle/brake linkage, and it sounds like you have some binding in the front diff. if it were me, being your waiting for parts id pull both diffs apart to inspect them. also wouldnt be a bad idea to pull the top cover off the transmission and have a look in there too, just make sure everything is in good shape.

untill the truck will roll smoothly dont even bother firing it, its just gonna burn up another clutch