I figured I'd chime in with my 2 cents worth of information. I refilled my 1988 with Redline 75/90NS and I noticed a significant difference in the shift quality. Before I was rarely able to get a good shift into 2nd without a grind (I know my trans needs rebuilt), but with Redline I very rarely get any grind at all. The entire shift process feels smoother in general. Much better than I expected!
Adam -- 1988 Alfa Romeo Spider Graduate