I like National for springs, but I think it's best, and cheapest to get an entire "package" from a suspension mfgr. for long arms. If the truth were known, probably many are Nationals anyway.
The only thing I don't suggest is using their shocks. Sure, they are OK, but I've found using RS9000's - adjustable, is the best way to go. You need different settings on and off road.
Any "kit" maker that supplies spacers or blocks should be avoided like the AIDS.
Trying to piece together arms from one place, arm mounts from another, springs from another, etc., will only get you problems. Some of the cheapo kits do exactly that.
Now - if you like the stock suspension and want to keep costs way down, you can go with the National springs for a bit more height, then strengthen the upper and lower arms so they can take the off-road punishment.
Seems like I posted some pics how to strengthen those arms easy, just takes some welding.
But still you end up with short arms, so the ride is sacrificed.
But it's a Rubicon, seems terrible to go cheap on it.