A proper spoa is going to give you 4-5" of lift.
Lowrainge sells a pretty good long travel shock kit...I recommend it.
You will need a track bar in the rear to controle axle rap.
High steer in the front to controle bump steer.
3-5 degrees of caster on the front axle is needed or it will wonder like a pig.(don't just weld the new spring perches on the front axle parallel to the existing ones). There are several articles detailing how to do this posted on this site....
In the rear set your pinion angle parallel to the flange on the transfercase.
Yes drive line extensions are a good idea. As are long brake lines.
Air bags in the rear will solve your loading issue, without screwing up the rig while not under load.
Your tire size should work well with this lift , But I also highly recommend a new stronger transfercase mounting system.
The stock mounts wont last with any lift tire combonation.
I basically have done all of Thea's modifications, and many more, to my 88 . If done right it works real well in the woods.
...Boxcar...