the mount kit for the Pro Comp Transaction Bars comes with a bottom plate. Yes, your U-Bolts go through the new bottom plate. The width of the leaf spring; however, has nothing to do with this. If anything is a concern, it is the length of the U-Bolts. I believe the stock U-Bolts are long enough to make this work. I have a Pro Comp Lift installed so didn't need to worry about the length of the U-Bolts.

 

Not necessarily. The u-bolts don't fit over the leaves, they fit around the axle tube. There's a bracket that goes over all 4 u-bolt threaded ends; this bracket would make the difference for the traction bars if the traction bar mount get sandwiched between the leaves and u-bolt bracket.

 

My $ 0.02.
If you have lowered, you should take your truck to a drive line shop to have the pinion gear / trans realigned. I payed $ 80, and it solved the problem.
I later added much more hp, and had to cure the wheel hop again, but with the Lakewoods that hwm3 shows. They bolt on in an hour and work fine.... I sparyed black on the yellow snubbers though.
If your axle is on top of the springs, muscle car type traction bars, which do not need as much height / space , no axle to go around now, should fit. The spring width is the concern.
I suggest Summit for the more generic parts. You can call and talk to customer service, and they will usually have or find the info you need, like U bolt width.

 

These are the bars I'm referring to, not the ProComp bars.