I used to travel with an SAS 1989 Toyota. Still have it actually, but it's been retired and will eventually be sold off. Replaced it with a Land Cruiser FZJ80.
The reasons are many. I too, can't really stand IFS, although I reconize that there aren't that many places a well designed IFS truck can't go that a solid axle rig, set up for expeditions (as opposed to all out buggy dedicated 4 wheeler) could go. Just look at Scott's Tacoma for example.
But solid axles do bring things to the table like beefier and more reliable axles, steering, and at least an easier time tackling obsticals.
The biggest problem with SASing either the older Toyota trucks or the Tacoma is that it's very difficult to build them using stock or even moderate lift hieghts, which it sounds like what you're interested in doing judging by your tire size. The reason for this is that the IFS frames of the older and Tacoma trucks are not arched properly for a solid axle up front and therefor, extra lift is normally used to compensate for this. Most SAS lifts are at least 5" with many being 6" or taller. That's a lot of lift for a Toyota truck. I was able to get mine down to 4" and that was the absolutely lowest I think one can go without cutting into the frame, which not easy or cost effective. I think the Tacoma's front frame arch is even worse than my truck, not to mention other issues with SASing a Tacoma that make it less cost effective or easy compared to the older trucks.
The other issue with SAS trucks is that it's almost impossible to add sway bars...at least to the front...and combined with high lifts, this leads to somewhat unstable platform for carrying heavy gear and especially roof top gear off road.
Now, this doesn't mean an SAS Toyota can't be used an expedition truck. I certainly drove my truck all over the place, at least around the Pacific Northwest and it worked, but it was a serious compromise. For us, we rarely tackled the extreme trails that it was more suited for, and so the compromise in highway handling wasn't really worth it.
I ended up going with Toyota Land Cruiser FZJ80, which allowed me to upgrade to a larger vehicle, with more power, larger and better sealed cargo space, but most importantly, most the off road advantages of my truck with its front and rear solid axles, but the comfort and handling of a modern SUV. Other than horrible gas mileage, I absolutely love it and I'm never looking back.
But if I were to built a Tacoma (which I almost did) I would do something like Scott's build and that means keeping the IFS, but giving it a minor lift and beefing it up as much as possible.
That set up will still go pretty much anywhere that anyone who isn't driving a dedicated trail rig would want to go. But most importantly, it drives and handles decently on the highway and dirt roads. Because let's face it. Most of us, spend the vast majority of our time on the highway and dirt roads, rather than extreme trails. So it only make sense that our "expedition" vehicles should be a reasonable compromise between good highway handling and off roadability.
Now, if you insist on solid axles and a Tacoma or like style truck as an expedition rig, I would recommend finding a rare '80-'85 factory solid axle truck or 4runner and putting a Tacoma motor in it. Not cheap, but you'd get the best of all worlds. Of course, you could also consider a Land Cruiser FZJ80 as they are coming down in price and would really give you the best of all worlds. So long as you don't mind worse gas mileage than a Hummer.
Good luck.
