I would suggest upgrading the level of components, not the vintage or # of speeds. Shimano 600 6/7 speed cassette hubs have taken a lot of abuse and continued to perform for me over the years. Although more expensive, Dura-Ace would probably perform even better. Also, you should install chains and cogsets together, pre-stretch them for a few hundred miles, and put them up as a mated set. That way you have a mated drive train ready when your current wears out.