Transmission swap

From the information I can find the 2003 and 2004 Isuzu Rodeos use the same transmission but no other vehicles interchange with that because of them having the 3.2 engine and they stopped building them in 2004 and they switched to a different transmission in early 2003. If you have the earlier build with the GM 4L30E in it there still are limited options because of the 3.2 and being 2WD.
However both transmissions have rebuild kits for them and most internal parts are available.
What is the issue with the one that you have that you wish to change it?

The internals are almost the same but almost doesn't count for much in this case as they are geared different. I would find a true transmission shop, they should be able to rebuild your transmission using the correct parts for the V6. Or build one even stronger.