I went looking for them online and I couldn't believe how expensive they were, I figured it wasnt right, same goes the air cleaner lol. I mean not that they are super expensive just much more than I thought.
Oil fill tubes in the valve cover are a 1968 and up thing. From 1955 through 1967 V8 engines had an oil fill tube in the intake manifold.
I still have my steel oil fill spouts designed to cut the top of cardboard oil cans with a steel top and bottom that would drain oil down that tube. When the 1968 sowed up you had to hold the can instead of clean the customers window at the service station. If you tried to force the oil spout into the valve cover it would be hit by the rocker arms and kick it back out spilling the oil all over the engine.
It took two service station attendants to sell oil and service the car so we stopped checking the oil or told them it was time to change the oil because it had oxidized. Around 1970-71 the plastic oil bottle with the "built in funnel" top arrived on the scene making our old oil can display on the gas station island obsolete. They wouldn't stack into nice displays so we couldn't entice customers to choose the high priced spread of motor oils that we put on the top of the display (the one that had gold foil on the label, instead of a plain white can with blue lettering for the straight 30 weight oil and no fancy name on the bottom rack).
It saved the factory a dollar or two to loose the oil fill tube but it made service stations disappear. Without a pump jockey looking under the hood at every fill up it became nearly impossible to sell real profit makers which were TBA items that included topping off the oil level of customers cars. We checked V-belts for cracks looked for fluid leaks, and even checked the air filter in hopes of selling one.
Now we have gas stations where no one ever raises the hood. Instead they buy donuts and cigarettes.
Of course I also have my one quart glass jar that had a screw on spout top that I used to unscrew and fill with motor oil from a 55 gallon drum from the time before quart cardboard oil cans.