How's the frame and rear axle housing?
Got one in the shop now that looks pristine from the top with just over 100k on it....but needed a few grand in frame repairs. You gotta watch the frames on those things...even if your not in the rust belt you never know where a truck that old spent it's time. Being parked outside in a shady damp spot on the regular for 20+ years is more than enough to cause problems even out of the rust belt.
Other than that, do what others have said...timing belt/water pump/pulleys (Oem or Aisin parts only-no aftermarket) and new cam/crank seals while in there at that age.
Change trans fluid with oem spec fluid and do so every 50 k
Make sure transfer case shifts properly and cycle it through the ranges once a month...transfer case actuators are expensive repair.
If your not mechanically inclined I'd strongly suggest paying a reputable shop for a thorough inspection abd check over before making your decision.
The engine in those trucks is hard to kill, but age more than mileage does cause some other moderate to large problems.
If its a 90k cream puff that was garaged and not in the rust belt, it's likely a solid contender for the 300k+ club...but its still a used 90k mile 24 year old truck...anything can happen.
Not sure what you gave for it or your finances, but having a spare vehicle around is great peace of mind. You can keep miles/wear off the newer taco and use it for trips and what not and daily the tundra and use it for more abusive truck duties
