6-spd tranny to replace 1996 Taco 4x4 with 5-spd?

[Mollydawg]

I'd like to replace my 5-spd behind a 3RZ with a newer 6-spd, primarily because of the two top gears being overdrive gears, to reduce highway rpm. How difficult would it be to adapt the 6-spd to the 3RZ, and is the 6-spd considered a strong tranny? Can it also be used with one of your dual-transfer cases for moderate off-road use?