Can't blame the lift kit outright. One side has ok caster. Something isn't the same (or mirrored) side-for-side.
Here’s the kit I used. https://www.rockymountainsusp.com/l...wd/f250-f350/1980-96/186f2k-sk.html?c=308&i=0 The kit provided little 3/16s spacers that I put underneath the coils, you can see the little gold spacer in the pictures. Could those be removed to help correct the alignment? I just assumed they needed to be installed. Sent from my iPhone using Tapatalk
High spring height = Positive Camber \----/ Low spring height = Negative Camber /----\ In theory, removing that washer will reduce your camber but I don't think 3/16" will make a huge difference.
More spacer or spring will reduce caster also. Is your truck setup heavy on the driver side?(battery, driver, fuel tank, etc)