Your best bet for something like this is to take the driveshaft to a driveshaft shop. Most of them keep a pretty good inventory of u-joints on the shelf and they should be able to get the old ones pressed out and the new ones installed while you wait.

The brand most better shops use these days is Spicer. I think they're still US made too.

If your concerned about it or just want to make sure, the driveshaft shop should also be able to check the balance on the shaft. After all those years and miles it might not be a bad idea.