I was listening to that metallic sound on the 65. Is it possible the fan is rubbing against something, I know you replaced the bearing. May sound funny but I've used a length of tubing or hose to listen up close to isolate where a noise is coming from.Staying clear of the belt and fan while running, of course. Off topic: Looks like we have similar chests from way back. Mine belonged to a colonial in the U.S. Army dated 1936. It has the wooden divided drop in organizer, for lack of the correct term.Heavy! You've inspired me to pull my Hoovers out from the moth ball fleet and tune them up! Again, nice collection.
The sound that your 65 makes may be due to new motor brushes that were installed before you got it. I would ask the seller if you can. They may not have disclosed this when they sold it. Wouldn't hurt to ask.
If the brushes are new, it will take a little bit of use for them to seat properly and the higher pitched sound to lessen.