i've said this before d i'll say it again. there is such a thing as "too low". i call it "stupid low".
in minitruck or something with a high reving engine, you might want to consider going with lower t-case gears or a doubler due to the fact that you might not have a lot of low end torque but you can rev the mill up to 6000 rpms. so if you're in low gear and need to pick up some speed, you can get on the gas and do so.
that is not the case in most cruisers. the inline 6s and even most V8s have plenty of low end but they won't rev up very high and take their time getting there. so if you're craling in low at 120:1 and need to pick up wheel speed quickly to avoind slipping off a ledge or other obstacle, you're pretty much out of luck unless you're a world champ at speed shifting and you have cat-like reflexes.
so i like to rely on a little torque to get me thru. here's a classic example. this video shows me driving greenfox's fj40 at katemcy just last month. the cruiser still has the original F engine ( never been out of the vehicle ) along with the stock 4spd trans, an orion with 4:1 gears and stock diffs. welded rear, arb front. fwiw, it still has stock axle shafts all the way around including the birfs. so the final drive ratio comes out to 56:1 which is not that low. the tires on the 40 are 36" iroks on cheapy steel rims. this truck is somewhat of a budget build and is still 90-something- percent oem toyota aside from the front locker, t-case and cage.
imho, it could use an h41 but nothing lower than that. it's very predictable driveable ad has no issues bogging down f you tap the throttle at he right time to bing the rpms up just for a sec. you be the judge:
YouTube - katemcy rocks red fj 40 in v notch part 3 of 4
there are 4 parts to the clip if you get really bored........