Based on that, I guess maybe you only need the input, 2nd and 3rd gear and the cluster.
In regards the the reverse idler, I'm not saying it absolutely has to be swapped. It was only a suggestion to make sure a problem doesn't happen and the trans has to come out again. Makes sense that the reverse idler wouldn't change, but I know the parts trans I have had a different slider/reverse gear than the one that was in my good trans. But both of those were OD trans, and the parts trans was a truck one to boot. So, just a thought.