When you put the spacers in the back, it will extend the length that your shock will have to travel, so you need a rear shock designed to handle the extended length. Bilstein's are probably the best in terms of ride.
Keep in mind when you start changing suspension parts, you'll have to do a wheel alignment. If you never had the front control arm bolts replaced with camber/caster bolts, you may end up needed these:
https://www.4x4parts.com/i-18981115-pat ... nsion.html
Hopefully, the bolts are seized to the control arm bushings, or you'll be looking at having them cut out and either replacing the bushings or the control arm. The same goes for the rear.
As you get to 2" and higher lifts, rear wheel alignment gets tougher to get into spec during a wheel alignment. If you run into that issue, you'll have to get offset, rear control arm bushings installed to get it within specs.