Worked thru the exact same quandary a week and a half ago, on a K1100RS with a leaky rear main. Oil had soaked the clutch, pressure plate, and housing. I personally would have replaced the clutch plate and cleaned up the cover and pressure plate. But the clutch cover had bent pins, so the owner wanted to replace that as well. Then the parts place he bought from in Chicago told him he had to replace the pressure plate with the cover, because the cover and plate were a balanced pair. So said the parts guy. Makes zero sense, because the housing is part three and that's not sold with the other two, and it's supposed to be at 120. Anyhoo, at great expense he bought all three: clutch plate, pressure plate, cover.
His Clymer said to set the marks at 120 degrees. There was no physical way to get the cover and pressure plate marks at 120. Could not be done. Only so many ways to do it and we tried them all. There was a clear paint mark on the housing, too, and attempting all permutations could not get even close.
Called the Chicago guy. He insisted that, yes, you have to go 120. Until we suggested he take the parts back, when he suddenly backed off and said do your best. Called Hermy's in PA -- the owner's shop of choice. Same song and dance. Finally called Charlie at TransAm in Lititz PA -- my fave place. Charlie said: "Bullshit. They say that, but they almost never do." Said: "Those parts are individually balanced. That's why you see those holes drilled in the one plate and the bosses ground off on the other one. That's when they balanced the castings." Said: "I have put hundreds of them together and any more I don't even worry about it." Said: "If they weren't balanced, that bike would shake like a dog shitting razor blades."
At this point we had wasted an hour and a half puzzling over the unpuzzlable. So we slapped her together no prob. Practical advice trumps correct advice any day of the week.