My suggestion would be to stay away from the body lift all together. It does not have a great look when it is done and it will give you a lot of body roll, especially with stock springs. The axles are not going to hold up to the torture that the 37" tires will put on them, plus you are going to spend a small fortune re-gearing the two axles once you get the large tires on it. If you don't then you will be going for a tranny rebuild real quick. I am just finishing up an "87" YJ build for my son and I installed axles from an "87" F350. They are 1 ton rated, already came with the 4:10 gear ratio that I wanted and I picked them up from the salvage yard for $200.00 each. I put a little extra in them to clean them up with new bearings, seals and brakes, but far less then what you will spend for new diff. Also these axles are much wider than the stock Jeep axles. This will give you a ton more stability on the road as well as off road, especially when you are going that high. I went with the 4" lifted springs that are a bit stiffer than the stock springs and installed them on the top of the ford axles. The nice thing about using the ford axles is that they are already set for the springs to be mounted on the top, just need to make adjustments to the spacing with the spring perches. By going this route I was able to get about 10 inches of lift without doing a body lift and the Jeep is much, much more stable and durable. It will probably cost you less this way in the long run as well. If you go this route I made some suggestions below as to other things that need to be addressed and in most cases these will also need to be addressed regardless of what lift you go with when you are going this high. You can PM me if you have any questions, I would be glad to help. I can also let you know what items I purchased and were. I can also email you some pics of what my 87 looks like with the lift since I can not add them to this.
1) All flexible brake lines need to be extended.
2) You will need to install a new CV style driveshaft in the rear and most likely a new driveshaft for the front.
3) Install a drop pitman arm on the steering box.
4) Suggest that you install a high steer arm on the passenger side knuckle. This will level out the linking arm and eliminate any bump steer.
5) Suggest that you install a new linking arm and tie rod. You can get 1-1/2" tubing, ends and new Heim joints that will needed to be welded, or you can buy them pre made. It is much cheaper if you can do the work. The large tires will make the stock ones flex and eventually fail. If you go with the Dana 60 front axle it already has a much thicker tie rod as stock.
6) Steering box support bracket, to keep the stress off the steering box bolts and the frame.
7) Extend the sway bar links.
8) Suggest that you install a drop bracket on the frame and a lifting bracket on the front axle for the tracking arm. This will level out the tracking arm. Most people remove both the front and rear tracking arms, but I kept my front one for a little extra stability.