Muncie Rebuild opinion
I've rebuilt a few Muncie 4 speeds and every single one has had good needle bearings in the cluster gear shaft. That shaft is a pain to remove and loading 120+ new bearings in there is one of the easiest jobs to mess up. I've done it plenty of times, and have it down. I've read a bunch of opinions that the original needle bearings are good quality U.S.A. steel and the kits now come with cheap non-U.S. steel.
So, what is the opinion here on leaving the cluster? The current trans I'm rebuilding was sitting in a garage since the late 70s. Every edge is tight and I know it has never been apart. Every gear is perfect, even the reverse. This is the sharpest 4 speed I have come across. The cluster gear even spins nice and freely with out binding.