[72HuggerK20]

Depends how "correct" or "show" your truck is going to be, but myself, I'd much rather have the underside and wheel wells done with black undercoating than paint. It's your truck, you get to decide how you want to do it. It's not up to anybody else to decide if what you did is right, unless that's your goal.

The benefits of undercoating the wheel wells would be that if a rock hits it from underneath, there's less of a possibility of it cracking the paint on the inside of the box. Also, sound deadening is a plus, but not really necessary on a pickup box.

Of course, epoxy primer under any sort of coating you put on that pickup box would be a good idea.

I personally did the entire underside of my cab, box, front and rear wheel wells, and the inside of the box with U-Pol Raptor Liner. It has held up pretty well to rock chips, and only has a few scratches that can be touched up pretty easily in the box. My box does have a steel plate floor that was welded in over top of the original wood floor, and I was not in the mood to mess around cutting that out.

Also, I lifted the box and cab up with a forklift to spray underneath them, and crawled in the box and worked front to back to paint the inside. Not sure what kind of equipment you have, but that worked for me.

Basically, do whatever you want and let the nay-sayers complain. Again, who cares, it's your truck, do what you think looks good and will hold up to the way you plan to use it.