Andy, I was more looking towards a metal stand off the valve cover. I can clearly see the cap, but its pretty much down in a hole. I can always use a longer spout funnel, but something attached and remains there would be nice. The hole in the cover is about 1.5" in diameter.

John, did the one on your 5th Ave press into the cover, or did it lock in with a 1/4 turn? There was an era with Mopar where the oil fil cap was rubber that pressed into the cover. I did see it had the push on cap, I'd be OK with that.

What I remember of the rubber push in style, the whole was round, and the cover surface was smooth on both the top and bottom surface. Since the cap on my cover is the 1/4 turn in and lock style, so the hole has the notches and the has the raised edges (inside the cover) for the lock tabs to pull tight against. I'm not sure the push in style would seal to the cover, or be secure once in the hole. I did see where I could buy an extension with a rubber "O" ring, that was the push in style for GM motors too.

I could buy a new oil cap and build my own fill extension, if it comes down to that, but buying something would be a lot easier.

Thanks for the help so far, I'm still looking at options. If someone has a fill extension on their motor, real pictures and measurements, and where I might find one like yours would be helpful. Thank You.