I would say you don't need much downtime if you are really organized. It could be done in a weekend with careful planning.
However, I am not organized nor am I a good planner, so if I ever decide to revamp this project or even have to do a HG, I think I've decided to buy a cheap 4runner or the like as a 4x4 beater while the 80 gets work done, then sell it when the 80 is back up and running.
I am also not a planner or organized haha I have so many bolts in a 5 gallon bucket from all my mechanical work that should have gone back into my 60 when I worked on it. Ironically enough I say that while sitting in a Toyota dealership getting my oil change done 300 miles ahead of schedule and not 6 months and 6k miles over due.
A lot of it is funding and I would need to buy new tools in addition to replacing what I am missing. I doubt its in the cards for me unless I get a second rig again.