RE adj control arms

I bought a set of second hand adj upper and lower control arms and I'm going to start installing them. They will be installed with RE 4.5" springs so my question is how do I know what length the lowers should be? And what should the pinion angle be at so I can adjust the uppers accordingly? The front axle is a HP30, I will not be adding drop brackets and I do have a 1" t-case drop kit.

You're going to have to play around with this.

Keep adjusting the lowers until the axle is centered (or stretched a bit to keep the tire out of the back of the front fender).

Once you have that, I'd say shoot for caster > pinion angle. You'll want about 5* of caster (use a level on top of the upper ball joint as an estimate). To gain caster, shorten your UCAs. To gain pinion angle, lengthen your UCAs.

You basically want to find a happy medium between how little caster you feel comfortable driving with and how much vibration from the front driveshaft you care for. Gonna be tough with no lockout hubs.

The double-cardan on the front driveshaft, the front pinion is supposed to be inline at the same angle as the driveshaft going to the transfer case, ie the pinion pointing right at the front output. However with the RE 4.5" that setup is going to give you a really steep caster with some steering issues as a result. Unfortunately changes to one affect the other so you will have to compromise--find the angle that doesn't give vibes on the front driveshaft and still steers okay. Depending on expected usage, one option is to remove the front driveshaft when on the street, and essentially ignore pinion angle.

i just adjusted mine so that the pinion angle is at the lowest it could be without giving me vibes on the street.

You might go to rcountrys site and look at there directions to set the i bought a 6.5 and want to say it was supposed to be like 17 eye to eye the instructions on there site should tell you about where to set.