My honest opinion here would be to save your money, do 2.1" instead of 2.8". You can continue to run the factory uca's with 2.1" with absolutely no issue at all. With a slight rake with the rear at factory height.
If ride quality is a must, definitely don't go over 2.1". Honestly, I would go for one setting lower than the 2.1" if you haul, so you can keep a little more of a rake, and maintain some ride quality.
The money you would spend on uca's or rear spacers, I would get a hellwig rear sway bar, and some rear end lower control arms from
Clayton or core. Depending on what you're hauling, I woukd get an equalizer and some air bags to put in the rear springs...
HOWEVER, if you're really not concerned with price and really want to go with 2.8" up front and UCA's. I would get zone or jba uca's, then a set of super lift rear springs to keep your rake while towing and to increase the rear by 1", they state it's 2" of lift, but they settle. Then I would get a one inch rear spacer, the Carli rear drop bracket for the panhard bar so you're ride over bumps keeps the rear from swagging around. You will then want some zone extended sway bar end links for the rear. Just to keep the sway in the back under control with the right geometry while towing. If you're very particular like me lol... but, to keep it simple, I would go with what I first said above