Having run the 6" spring on an '88 Waggy here are my thoughts. Those spring run pretty stiff. It will depend on whether or not you wheel it as to if you will like it or not. The more you wheel it, the more you will want to go another direction. Whether or not you go 6" spring lift or SOA front and shackle flip rear, here is some of the stuff you will need to look into;
1. longer rear emergency brake cables from frame to axle. The stock ones can be backed up 1-1.5 inches by relocating the frame side mount rearward, but for some that isn't enough. J-10 rear cables are longer than the waggy ones so that is the option I run.
2. Those front springs will require a longer shackle to prevent the shackle from inverting forward (getting stuck under the front bumper) as the spring compresses ie gets longer. Unfortundately this lifts the front even more and makes your caster angle worse too.
3. The front driveshaft will be operating at or near it's operational angle at the constant velocity joint at the t-case. Some (me too) need to run a clearanced CV known as a high-angle cv. Also, the transmission crossmember will need to be clearanced to allow the front driveshaft to droop far enough down without hitting it. Many have cut and frenched in a piece of steel tubing. Search for some pictures and it will make sense once you see it.
4. Longer brake lines front and rear.
5. Even with a drop pitman arm, the steering angle of the drag link is nearing excessive. Long term you will want to look into cross-over steering to straighten it all out.
6. 35's are really tough to fit on a waggy without serious cutting. Another option would be to run a 33x10.50r15 tire like ones that BFG sells. Can maintain the stock 15x7 wheel with these and they fit up in the fenders easier. If cutting the sheet metal doesn't scare you, 35's can fit all day long.
7. Longer front bumpstops will be needed to prevent over-flexing the springs and to keep the tires off the body. The rear bumpstops were probably never hitting the axle anyway and I have never extended mine.
8. You will more than likely want to install a set of manual locking hubs up front so that the front driveshaft can stop spinning when disconnected. The front driveshaft angle will be pretty bad and it will want to vibrate on the highway.
Personally, having owned FSJs with the Skyjacker 4" all spring lift (still running those springs), a FSJ with the Bj's 6 spring lift, and various versions of SOA, SF and such, here is what I would do. I would either run a Skyjacker 4" full spring lift + a 1" body lift, or go straight to SOA/SF with new stock packs. If height is your primary goal, I would go SOA/SF since most of the things I mention above, need to be done for the 6" kit or the SOA/SF anyway. BJ's site has all the SOA/SF kit stuff too so check 'em out.
'78 Cherokee Chief: 360/TH400/NOS QT, '04 Grand Cherokee: 4.7/545RFE/242HD w/SYE, JK Rubi front axle, 4.56 gears, Protofab rear bumper/tire carrier