This exactly, and an NSG370 would not be my first choice if the sky was falling and I had to convert a 32RH to a manual transmission which I consider to be a downgrade.
If you absolutely must convert, convert to the much better quality and stronger Aisin AX-15 transmission.
If it were me I'd consider converting from the nearly bulletproof 32RH to any manual transmission to be a downgrade. And it's my opinion that you wouldn't be saving any $$$ by converting to the manual over simply having the 32RH rebuilt by a competent/good 32RH rebuilder.
I went the other way, I converted from a 5-speed to the 32RH solely for the huge benefits like 2-3x greater low-end torque and infinitely low first-gear ratio you get with the 32RH. Automatics are the choice of serious rock crawlers.