I've rebuilt two of the narrowblock KM132's at this point. This guide from Starquest club is extremely helpful: https://www.starquestclub.com/forum/...-transmission/

The internals between the wideblock and narrowblock are the same as far as I know, I have two narrows and a wideblock from a Starion that I am going to be using for parts. Either way, you should be able to use the good parts out of whichever transmission does not fit in the one that does, if necessary.

That being said, both of my rebuilt narrowblocks have failed (One was my fault, didn't resurface the mainshaft to save money and it's now making confetti in there).

If you do decide to rebuilt, it really isn't that difficult. Hardest thing is staying organized, and getting creative without the right tools. If you decide to go that route, I've learned a couple tricks that may come in handy