on my 56 - i had a random squeak when i turned the steering wheel - was driving me nuts. the cause turned out to be a 1.5" long spring with an OD of 1" and an ID of .750". It went on the steering shaft and ran on the surface of the mast bearing and the back of the steering wheel. It also is not shown in the assembly manual. I don't know if it belongs there or not. It is in compression when the steering wheel is installed, exerting light pressure on the mast bearing and steering wheel and may serve the same purpose as a lock washer on the steering nut - but I'm not sure. The squeak occurred when the end of the wire forming the spring scraped on the back of the steering wheel. I added 2 copper washers and a little grease and that stopped the squeak.

so - does your spring fit over your steering shaft and could it go in the same place? I am unfamiliar with the 60-66 series...