Kfd, you’re working with a couple misconceptions here.
1. There is zero need or benefit to adding airbags to the front of the truck. Unsure what you’re trying to accomplish unless you feel the front springs are so tired they’re sagging.
If that is the case, bags are a bandaid and a poor one at that. And likely springs cost about the same, and relatively easy or cheap if hiring out the work, to replace.
2. Don’t obsess about measured fender height differences. First, spring rates are not different side to side, as designed, to account for minor weight differences such as a fuel tank. Second, your truck is 22 years old and admittedly has a tired suspension. Even if it didn’t, many/most pickups and many other vehicles have slight ride height differences. I’ve had probably 30 pickups in as many years and been around or responsible for hundreds of trucks. Many of my personal trucks have different ride heights. Part is loading, part is any anomoly in the surface where parked and most of it is trucks just don’t always sit perfectly the same. 2-2016 trucks and 1-1986 truck in my driveway. 1 stock, 2 lifted, all 3 sit a little different side to side, as did the last couple 2007, 2008 and 2013 models. I can notice a 1/2” difference by eye pretty easy and most every truck is a bit different.
To your actual question, if you only need 15 psi air, you really don’t need the extra support, however, I’d air em up more, where once you drop the trailer on and the set the wdh you get back close to unloaded rear height. (With it riding higher than normal height first.) This’ll help a bit if you’re sure the rear springs are sacked out some.
Sounds confusing but you’re on the right track imo save for the front airbags.
And yeah some trial and error setting up will likely be needed to get it dialed in.
But the rule of thumb still stands. Get the front back down about to unloaded height and that’s real close to right.
2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold