The license tag on my 1973 1/2 R75/5 reads "Expires 6/30/89" - and it's been sitting in the garage ever since. I'll be cleaning it up this weekend, then making arrangements with the local dealer to pick it up for restoration.
I was a BMWMOA member from 1976 to 1986, and had some help from CRBMWMOA friends converting to a disc front brake and double plugs. Other "blasts from the past" include a Windjammer III fairing with lowers, a Teutonic QSL solo saddle, and Craven bags.
I've been out of the world of two wheels for the last 15 years, and suspect there may be other worthwhe products to consider. Are there any any additional upgrades you might recommend?
You might be surprised to find there isn't much left to upgrade on the old /5. Plenty of airheads still running around with windjammers and craven bags (the bags are starting to be worth some $ as time goes on). There are a couple of fairing companies out there, Parabellum and Aeroflow come to mind but I'm not sure they would be a real "upgrade" to the 'jammer. Hannigan makes (made?) a nice fairing but they are hard to come by and big $. New shocks and springs are what I would suggest in terms of bang for the buck, plenty of advertisers in the back of BMWON.
Biggest change has really been in the connectivity of the world. Check out ibmwr.org and the airheads beemer club (airheads.org?) for more tech information than you possibly absorb.