Most of those MT fluids are the same. GM (Texaco) MTF along with the Chrysler equivalent are both 5w-30 with a friction modifier. It was developed for the New Process transaxles in Minivans and K-cars. It’s good in all NP/NV transmissions and transaxles except the NV4500. Honda MTF is very similar.
You can use synthetic as long as it’s friction modified for synchros. I use Amsoil MTF for MTF applications. Amsoil ATF for ATF applications. For gear lube in a trans I use what’s cheap at NAPA or TractorSupply (gear lube isn’t high-tech).
Gears like gear lube. They are quieter and will last longer. Worn synchros like gear lube. Low clearance needle bearings do not like gear lube because it doesn’t get in there. Needle bearings in older units designed for gear lube do fine with gear lube obviously. Some older trans specify “all mineral” 90wt which means no EP. Chains do not like gear lube because it doesn’t get in the pins. If you have a NP203 run gear lube in the drop box and ATF in the chaincase.