Thanks for the great feedback all! There's a couple pictures of the old Holdsworth in this link Holdsworth Frame Numbers The actual thread has more info about purchasing the bike in 1974. It's not going anywhere. It will burden my heirs along with all my other obsolete technology that's not worth selling and too cool to get rid of: wood XC skis, tube audio gear and an MG Midget, etc. etc. etc.
That said, the appeal of new bike is that it's turnkey: Air in the tires and go. I tell myself I will ride it more. In theory the Holdsworth could be too, with (as pdlamb notes), an infusion of cash, but even back in the day it was more a skittish thoroughbred rather than a daily driver (to badly mix my metaphors). A nice, and fast, ride but not really an easy one. I haven't gone to ride a new bike, mostly because I'm afraid I'll like it. I think I should try one out.