Any old bike that is saved from scrap that isn't anywhere near original but can be fixed up to ride is fine. I don't ever endorse cutting up a good original, but many classic bare frames can easily be made into a decent rat. Most of the old stuff I got is free, so it's pretty bad off, seldomly with original paint worth saving. My 53 Schwinn, the bike I first ratted out in 1978 was so badly pitted from rust on the chain stay that I filled it in with bondo, still has many miles in it, but not as a restored Meteor. Not worth a complete restoration, but still beats anything made in China. It's had different versions over the years and the frame waits in a shed for another rebuild back in Florida.