81 means it's an L50 5-speed.
My advice: buy it, and huck that POS L50 before it blows up on you. L52 will be a direct bolt-in, and will be far stronger than the L50, which was a modified version of the 2WD transmission, and not built for the higher diffs.
First-gen stock gearing 4.11, maybe the previously mentioned 3.9 is a dealer mod, or a PO mod, but that's a way obscure ratio, Most North-American Toyota 4X4's of that era (basically the Hiluxes, FJ40, FJ55, FJ60) had 4.11's and rarely had 3.73's.
These are not Tacos, but are better IMO, they're solid front axle, they're simpler, and lighter. The 22R doesn't have a Tacoma's power, but is pretty much the motor that gave Toyotas the bulletproof rep; and if you wanted to Tacomize it: a 3RZ-FE, or 5VZ-FE will make it fly because it weighs nothing.
Modding these rigs are cheap, far cheaper than a 40 (I have both a 40, and RN38). They're a killer DD, great mileage for an old 4X4, fit anywhere, and impossible to kill, you'd have to crumple it up into a bal, and toss the thing off a cliff to kill it. They're the best-handling truck I've ever driven, they steer true, respond well, and can turn on a dime. My buddies get a kick out of The Mule's turning radius (or lack thereof), I can put the cab where the tailgate was almost instantly. This thing was made for windy, hilly country roads.
The 22R can be a surprising motor, mine never ceases to amaze me, it was stiff and gutless when I first got it post-rebuild, broke it in over a couple months, and she loosened right up; then I blew a hole in the muffler, and now she'd just amazing they didn't market the first-gen as "the Sport-Car of the Pickup World" for no reason.
Visibility is surprisingly good. I first thought First-gens would be blind wth how "deep" the B-pillars are, but the driver's seat is set so you have a perfect viewing angle over the bed, and the mirror is positioned to nearly eliminate blind spots. This truck has, by far, the second-best visibility of all the vehicles I've driven, nearly as good as my 40, better than my old sedan, better than my sister's Matrix and mother's F150, lightyears better than my Dad's Mazda, and no comparison to my old C10.
Clearance: with smaller tires and dead springs, my first-gen had better clearance than nearly anything on the road that's stock. I've had people ask me what lift I'm running, and get surprised when I tell them it's just saggy, stock leaves.
My big complaints:
It drives like a truck. Modern trucks with coil-spings and IFS are really cushy, and comfortable, this isn't. It's comfortable for me, because I like trucks, and anything else feels wrong, but it will transfer the washboards into the cab. Mine is especially stiff because the rear spings have an add-a-leaf, and the anti-wrap leaf stiffening things, and the fronts are inverted so there's about an inche between the frame and bump-stops, but I'm not far from some OMES right now.
Cab space is tight. Again, far from a problem for me, I'm short, and it feels perfectly right, but it's similar in dimension to the front of a 40: shallow firewall, narrow cab. It still works, though, there's enough space behind the seats for speakers, a rifle, a pistol in a lockbox, and two bricks of ammo, it just requires some creativity to make it all fit.
Noisy: The cab is one of the tightest, most resistent to enternal sounds I've ever driven, the outside world is nonexstant to me audibly; however, all the engine and tranny noise goes straight into the cab. If you're in 4WD, it's like somebody's shaking a box of rocks under the passenger's seat. Soundproofing will solve this.
Transmissions are bothersome at times. Mine was pretty stiff post-rebuild, but after a couple hundred-thousand miles the bushings now have the perfect amount of wear to make it shift like buttah! They're noisier than a garage-band on a Saturday, however.
Suggestions: Get a Tach! I live my my tach, I'm not gonna lie. It's the most up-to-date means of knowing exactly what your engine is doing, and my speedo doesn't like the cold, and will not work in the mornings, however I know:
2500 - First gear - This isn't even classifiable as speed.
2500 - Seond - about 20MPH
2500 - third - 35-ish
2500 - fourth - 47-ish
2500 - fifth - 55.
The Mule can sit at 2500 Revs all day.
Good luck!
