"...A K-Mart bike from 35 years ago isn't going to have improved over that time and those bearings are probably going to be worth more than the bike new..."
I bought six 5/16" bearings for $4.15 at Ace Hardware. I needed nine bearings to fill the holder. So with the ones I found in the dirt floor I have what I need to put the bike back together. And some left-over bearings if needed in future.