hey, don't be addin' tech into this
Meh...I see one downfall on the 80's...and thats the headgasket that some people have problems with, and others dont

so you fix that and then there's no issues...
pesky heater hose...cheap fix, not fun...but cheap
has anyone ever had a timing chain break on a 1FZ?
I believe there are a few FZJ's past the 300k mark
and since we all WHEEL to work, and WHEEL every day, you're right...what do you need extra HP for?
thats right, the ability to actually merge onto a freeway ramp in under 14 seconds. ;p Or go up a hill that a bus load of dirty hippies in the VW van WON"T pass us
Don't get me wrong...the FZJ's have a lot of exra crap/fluff that's probably not needed...I mean...why toyota went to a more horsepower, full floater rear, 4 wheel disc brakes, Electric lockers front and rear is just BEYOND me

....again...I'm not bashing the FJ80's...
and tech...yes gear it if you are going to run bigger tires...ANY rig is going to feel sluggish when you start adding bigger tires.
BOTH FJ80's and FZJ80's start to feel that way when larger tires are added. Gears will help some and put some pep into the feel of the rig.
I would adjust that transmission cable, throw some gears and run the living piss out of the rig. For what you are wanting to do, it will do fine.