I tried a set of 35's(12.50 on 10" rims w/3.75 backspacing) on my '90(w/4" IFS lift) and they rubbed at full lock. If yours clear w/a stock suspension, you likely have a 3" body lift and cranked T-bars.
If you are familiar w/what oem IFS and lift kits look like for the IFS, here is a pic of an:
OEM IFS(angle of lower arm is due to 1.5" upper ball-joint spacer),
Traimaster 4" lift bracket IFS.
On my '91 I cleared 36's(the pic is with 35's) using a 2" body lift, 1.5" ball joint spacer, 3" longer rear shackles, beating the body seam back to the first body mount, as well as taking 2" out of the fender.
IIRC, you have an automatic, you will likely want to swap to 5.29's at some point down the road, the 4.88's that are in it are oem specs for 31's and an auto transmission in the v6 models. The 5.29's would still be out of spec w/ the auto, but it would help the performance of the 22re a lot, or swap in a 5-spd. W/dual cases the a manual transmission works almost as easily as an auto on the trail.
Seeing how guys w/SAS swaps have ripped the shock hoop out of the frame w/just the loads of the shock being applied to the hoop, I think you would need something a lot more substantial than the hoop since it has to support the weight of the vehicle, as well as all of the forces that are applied during on/off pavement use.
Total Chaos Fabrication has a kit that used coil overs, check them out and see all what is involved. It is a nice kit, but expensive for a trail rig that doesn't see a lot of high speed off road driving.
There have been a few attempts over the years of trying to make the IFS system work better for off-road, and most of them have proven to be expensive. IME, the oem t-bar suspension will work well enough, providing they aren't cranked to gain lift. I get enough wheel travel out of mine w/the t-bars set at oem spec and w/the sway bar disconnected to not have issues with the trails I run. Yes I have done my share of three wheeling, but you get used to it. With a locked rear you really wont have much issues for the type of wheeling you like/expect to do, to justify the expense of swapping the t-bars for coil overs.
Once you determine how the front was lifted, we might be able to give you an idea of what you can do to get a little more wheel movement out of the front end.
