About the gas caps, both my 67 and 68 Wildcat, 68 Le Sabre and 67 Rivieras have non vented caps. Just like Chris's 70 Skylark, it is also written "NOT VENTED or NON VENTED" on them. The gas tanks are vented by a rubber hose that goes over the rear axle. On my former 68 Wildcat, when the tank was full and the car was parked on a slope, the gas would come out of the gas cap as it didn't seal perfectly when closed and the filler was very low. This is unlikely to happen on a 64 as they have a side mounted gas cap.
