The only parts that are really worth your effort are things like axles. If you do it right, you will just be messing with wear items some day....Good luck maintaining a body and keeping its integrity from deteriorating over time if you're actually wheeling the truck hard, if you don't want to dent it, don't wheel it. Limiting factors off road should be things like, lack of traction, flotation, wheelbase, center of gravity, etc....not things like "I'll scratch my paint".
Not that I'm saying everyone should tear up their truck...I'm just saying if you're really serious wheeling, there is already enough limiting factors without worrying about sliding in to a tree or hanging up on a rock. Ever watched competitions? They only care about breakage...sliding, slamming, scratching...it doesn't matter so long as you're still advancing, and it's still difficult without worrying about all the aesthetic stuff.
If you aren't wheeling something that's all function over form like that, then money in axles probably isn't the right path to take, or at least isn't a necessity. If it's just a light wheeling rig that's fun to drive on the road too, you probably don't want a tire bigger than 37" and there's probably bigger priorities with money than an axle you can't break.