Can anyone tell me for certain what fluid should go into a 5 sp Manual transmission for this model? 1999 Honda Passort 3.2L V6, LX. I have seen both 5W-30 and Dextron III listed as the required fluid.

That was built by Isuzu, not Honda. Isuzu Trooper-Similar- recommends:

1999

Dexron III, ZF TE ML 09/14, Ford ESD-M2C138-CJ/ESP-2C166-H, Allison C4 semi-synthetic for automatic transmissions

Gearbox, Automatic

Go to the Amsoil.com site and enter the necessary data; otherwise, call your local Honda parts department.