I know I've seen a product somewhere that said permanent, I don't really want to have the tires remounted just for lettering.. I'm sure something exists out there
Unless the truck has been slammed almost to the ground, thereby blocking the "view", reversing the mount of rwl's tires will leave the 'whites' very noticeable...not a good look, IMO.
Way back when, we used DuPont's "Tire Black" to cover-up whitewalls, even mother-in-law 'curbed-walls'....haven't seen it in awhile, though. As with any product that was effective before the 1980's, the EPA probably had it taken from the shelves and replaced it with something less permanent. Rendering newer versions as useful dog pee.
The best remedy is still reversing the mount. But before you do, or have it done, contact:
-Ranger Labs...they have tire paints.
-Eastwood...try their brush-on rubberized undercoating.
-Wherever the tires are re-mounted they might have a version of "Tire Black".
I personally wouldn't use any products on the 'whites' unless the tires are re-mounted.
Unless you've already quoted the total price of the resto-job...add this to the total. Unless the tires are near the end of their life cycle...that's a different scenario.
Bob