On a bike that old I'm betting that your cones are pitted. If they are pitted even a little bit it makes you choose between loose and crunchy feeling.

People talk about going to your LBS and picking up a new pair of cones like they'll have a drawer of them. It probably won't go that way. There are a gazillion different cones so it's probably going to be a special order deal. Good luck.

If you can't find cones that are a pretty close replacement, you'll have to decide between slightly loose and a little crunchy. Ultimately replacement wheels are probably in order. After 20 years the rims are likely to be a little iffy anyway.