The rubber washer goes on top of the frame extension, the 2x2 metal shim goes on top of the rubber. The lock washer goes under the frame extension. If you have a shop manual, on page 1-2 is a picture of the front and rear mounts and instructions on how to addjust the cab height. I just went out and looked under my 54 cab. The rubber washers are still stuck to the bottom of the cab. There sure were a lot of black widows under the cab.

54 Chevy build pics.