Hi Morri, I had several of these apart. Thrust washer issues come to mind. Looking like you're going to have to do some detective work.
To be clear with nut tight the entire assembly turns on main shaft ok? But, the basket is binding on the cush drum. Is that correct? When binding does it seem to lock the main shaft to high gear. Meaning trans in neutral you spin clutch center & the trans sprocket turns too even if you hold it with your fingers?
I don't think you can assemble the drum inside out. I have more experience with later ones which have slightly different shape. The side plates are obviously inner/outer which only goes one way so I don't think that's the problem.
There are different thrust washers depending on the year. The washer must match the little hub that goes onto main shaft. Also the washer chamfer must go right way round. So all this must be matching set. I think later years will fit your main shaft, but I don't know how to visually tell them apart but the later washer is different.
Also the rollers must be measured for length. If too long they will bind. I've not personally seen this though. The ones I've bought have been to spec in shop Manual
Without being there makes it kind of hard.
How does the little hub fit on main shaft just by itself? Is it bottoming against the nose of the high gear?
On the bench can you wiggle/spin the thrust washer? It should be quite free.
Bolted up there is a lot of wobble on basket with all new parts. If you didn't know better it would seem too loose.
If needed you could use some flat washers, bolt & nut & simulate how clutch assembly is being pinched. Since it's on the bench you can see how the thrust washer actually is while parts are bolted.