Never really liked the idea of alloy nipples. Just too prone to corrosion and seizure, plus Aluminum is just weaker in the long run. The softeness of the material also makes it easier to round off the nipples when truing the wheels. I always stay with brass nipples when building up new wheels. they are a little heavier than aluminum alloy nipples, but way much less problems with them in the future. Good move re-building them with brass.
BTW, I agree about replacing all the old rubber on the bike, specially the tires, tubes AND brake shoes. All those would have aged and hardened enough through the years to negatively affect their performance/reliability. Also be aware that brake and derailleur cables also tend to get brittle through time, specially at the areas where you clamp down on them. They are so cheap to replace that you should just get all new ones for the whole bike.

Chombi