wheel build: reusing rim with new hub
 

The flange on my rear hub cracked, so I need a new hub. Since the bike is mostly original (and what's not is period-correct), I'd like to keep the existing rim and (hopefully) find a NOS hub to put in. (Don't really care about the spokes.)

It seems straightforward to me, but besides spoke hole count and dropout spacing, is there anything I need to watch out for on my search for a replacement hub? Is it safe to use a thirty year old hub which has been laced up once for maybe 100 miles? (I found what seem to be the same but older hubs on eBay...) What about NOS stuff that's been sitting in LBS display cases for 10-20 years?

Not building this myself; I will be finding a good builder to put the wheels together.

High quality old stuff is good as long as it is well maintained. As long as it wasn't run dry, you should be able to buy it, repack the bearings, and enjoy. If there are marks on the flanges, you want to lace the wheel to match those marks, otherwise you risk cutting the spokes.