Yes, first timer posting here. Nice site too!

What is / who has, the largest lift on a second gen 4runner? I'm starting to build a 91 4runner and I plan on running 39.5-15-15 or 39.5-13.50-15. SAS, Alcan is building my springs (8"), lockers and 5.29's are coming from Randy's and a ton of other parts are coming from Marlin Crawlers. I'm guessing I'm going into unchartered waters. I wouldn't think I'm the first so I was hoping to pick someone's brain.
Now, why so high? I'm in South Mississippi on the Louisiana line and we don't have rocks. We do have deep mud and its something I haven't ever seen before. Thats it in a nut shell!

THANKS!

 

Gibby (upndair) has a rig setup kinda like that...

 

Skip the Toyota axles and go straight to 35 spline 60's. Gibby will tell you the same. Even the 30 spline chromo super axles from Longfield likely won't last with 39's. Not sure how much tire the 4Runner rear can handle.

 

My Toyota axles and steering weren't standing up to 37" tire.
Mud itself is not hard on the axles, it's hitting the stumps and roots and such that are. You will not want to go more that 35s with a stockish Toyota motor - even with 5.29" gears. You won't be able to get the tire speed up for mud.
If you're getting a crawler setup from Marlin, you'll be in good shape for the slow running of the trails and anything else that benefits from going slow - even the 39's will work and the stock motor motor will do OK with a crawler.
Other issues to consider.
The 39.5" tires WILL require either a significant body lift and fender trimmin front and rear - or you'll loose a lot of articulation with huge bump stops.
The front axle will need to move at least 3" forward from the factory location and the steering box will need to be moved forward. The frame will need to be braced at the steering box.
Your Toyota brakes may not handle the large tires when you need hard braking.
With the large tires, you will require a traction bar or anti-wrap setup.
To fit the large width of the tires you'll need to use spacers and reverse offset rims. That additional stress will break axles and bearings. That's not a problem if you prepare for it and bring spares.
You'll need the latest and greatest Longfields or comparable to have any chance of keeping birfields together.
The vehicle will be very unstable with a high center of gravity on a narrow base.

There are people that do run 39.5" tires on Toyota axles. Reading your post again, I think you'll be very dissappointed in the result if you run 39.5" tires with a stock motor - and you plan to play in the mud. You need wheel spin to keep tires clean. You'll keep them turning with your crawler gears but you won't be able to spin them faster enough to clean the Mississippi mud out of the tires.