Go ahead and buy a rc shackle and a cheap 2" puck. You said you have a 3" rc lift the shocks are made for 3-4" of lift they will work. When you put it on put the shackle up at the full 2" if you got a add a leaf if you went with full packs then go with the 1.5" setting. Then take the stock spacer out. You will get drive line vibes the control arms will be angled more your axle will become less uncentered you can fix that by drilling a new hole for the track bar. I've done this and it works fine. Also your brake lines in the rear will be stretched so really this equals a mall crawler system and your flex will be limited by the control arm angle and depending on what size tires and how much trimming you want to do.

 

I was going to do the exact same thing...

however I ended up moving the control arm mounts back and running FRONT JK upper and lower control arms ($60 used local), Rough Country 1.5" lift shackles (junk yard $6), 4.5" Rough Country coils, new in box, (Craigslist, local $48), home made double sheer track bar, home made frame side track bar mount, steering stabilizer delete/axle side track bar mount beef up, used shocks, homemade shackle relocation boxes (got them right the first time), and a used slip yoke eliminator kit with a front D shaft in the rear ($60 used)


I ran a home made 1.75" spacer in the front for a little while...

I think i t flexes pretty well... I would put up some pics, BUT my photobucket account is not working...

 

He said he has a 3in and wants to add 1.5 for a total of 4.5

 

rc 3" kit shocks are the same as there 4.5" kit so if you do add 1.5" they will be fine. but your looking at all the extras when you get over 3". so save up

 

okay some people say the shocks will work and others say they wont, and im still not 100% on what else i need after the puck and shackles... sorry newbie lol

 

im telling u the the shock will be fine for now...what i did when i went from a RC 3" to a RC 4.5" i got on RC wed site and went to there scratch and dent and bought a set of 4.5" coils and i picked up one of there adjustable trac bar, then got a factory ZJ pitman arm its bout a 1" in a half drop witch meany says u dont but whatever, and then i got a set of factory 98 full size chevy truck shackles witch is bout a 1" in a half lift and i went to Rustys offroad and got set of upper and lower fixed control arms....ran that all on the RC 3" lift shock tile i got the money to buy the longer ones