Well if you are planning on doing rock crawling with 35"+ plus tires you will need to obviously upgrade the suspension, hi-steer, ifs steering box, brake lines, etc.
Generally the 85' 4runners will have the price jacked up just for what they are, but like 2ndgen said finding a 86-89 and doing all the stuff yourself might be better. 86-89 are generally cheaper, plus i would look for one with a 5spd rather than the auto.
An SAS really is not that bad. If it boils down to money I would just see how much you can find an 86-89 for a solid front end should be no more than $300 and you will already have the steering box. Then you just need spring hangers, grinder, and welder.
Or if you can get the 85 for a good price go for it! I just look at it terms of $$$.
Hope that helps.