My bet is the fuel guage problem is b/c of a diff size tank for 2wd vs 4wd truck?
I have this problem, swapped in a cluster from an '88 v6 4runner into my '89 4 cyl (both auto). Which btw required no re-wiring or anything.
My guage go all teh way down to empty and stays there a long time before the light comes on.

With 200+ Billion electrical parts, the world most complicated machine is inside your own skull.

Question Reality.
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'89 Rnr DLX "SR4.5", 32s w/ 5.29 locked f/r blah blah