With a 55.1, assuming it is the four bolt perimeter style, that cover is the one year only 54 cover. That cover does not use a baffled vented valve cover breather because the vents allow the breathing. 55.2 on the trucks, and all 55 and up motors, those valve covers have no vents and use the baffled vented breather. The earlier 2 bolt covers, had even larger vents.
The aftermarket use to sell a thick cloth arrangement that bolted to the center studs. Supposedly was to quiet the motor and catch debris and water. I have never seen anything for the 54 arrangement but that does not surprise me as it was a one year only cover. So I guess if you wanted to eliminate the four slots, you could braze them up and install a vented cap, or just change over to the later valve cover.
I would be curious myself to see if anyone has a baffle, cloth arrangement for the 54 cover.
