What size tires are you running? One thing you could do is run a bit larger tire. Your speedo will be off - It'll read slower than actual speed, but that's one way to get back to where you need to be.

Other options are sourcing axles out of an older 4 banger truck. 4.10s were available in the late 80s 4 banger HBs, and 4.375s were also relatively common. Look for CA41 (4.10) or CA43 (4.375) axle codes on the build sticker in a donor truck.

V6 truck axle swaps would be a good option for the rear, but the front has to come out of a 4 banger truck - your truck has an R180A front diff. V6 trucks had a larger R200A front diff that will not clear your oil pan.

The 96-97 H233b rear is a 2 pinion axle. Earlier units were 4 pinion. An LSD should still have been a factory option for your truck, or you could swap in an older 3rd member from a WD21 pathfinder with an automatic trans for the same gear ration and axle spline count and factory LSD.

Bottom line: The KA motor is underpowered for a 4000 lb truck and it was geared low to compensate, and to put the engine in its peak power band at cruising speed. The taller gears will bring those rpms down, but you'll have no power without downshifting a couple times. Is it flat where you live? If so, you can get away with it, but if you live in moutainous country like I do, you want as deep a gear as you can get in the axles. I'm running 5.14 gears in mine with 33" tires and it's still a slug on the hills.