Sounds like your right rear spring could be worn out. Or maybe the frame is bent, or something else. I would avoid trying to level out the truck by running one shock with much more pressure than the other, as this could hurt your handling.

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1999 XLT S/C, 4.2 V-6, auto, 3.55 rear, dark torreador red/harvest gold, bed liner, Sony 10 disc CD, Edelbrock IAS, K&N filter, Superchip

 

yes you can install separate inflation valves for each shock absorber. However it sounds like you need to have the rear springs inspected closely because something isn't quite right .

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Member: Never trust a person over 40 who drives a Chevy club
Flatheads ain't so bad!
Certified backyard mechanic I & II

 

It is the spring's job to hold the truck up. Springs do sack out over time - especially rear leafs.

Adjustable air shocks are great for some things, but correcting a ride hieght difference between left and right sides is not one of them.

 

I just installed 2 in. drop shackles on my 95 F150 and now the right rear is one inch lower then the left. I already have air shocks that have a single point valve for inflating both shocks. My question is this:
Can I install an additional valve to inflate the shocks independently in an attempt level the rear laterally?
Thanks,
Randy