The 54 valve cover was the first four screw valve cover used for the 235. The 53 and prior covers, these were two hole center stud hold downs and used vents in the valve cover itself. The 54 is a one year only cover in that it has four small slots (as opposed to the somewhat larger vents in the 53 and earlier covers, and used a non-vented cap. Presumably the concern was that water or debris would get in the top of the valve train through these small vents. So for 55-58, the vents were eliminated and the non-vented cap was replaced with a vented cap, in the identical location as the 54 cover. 59-63 valve covers were also 4 screw hold down covers, but the vented cap was located to the center of the valve cover. I happen to agree with the above advice, hang your 54 cover on the wall, get a 55-58 cover and vented breather and you are all set.
The 54 is the orange cover, the blue cover to the right is the 55-58. The next is the 59 and up. The last one is a Canadian Pontiac 261 cover, no script but otherwise 55-58 style.
