Technical Old looking Fuel cap for modern filler neck

On my build I used a modern filler neck with the screw in cap and now I am looking for a screw in cap that looks old style that will work with this filler neck.
I thought I would have no trouble finding one but so far I have not found any

 

could you fix the guts of a modern one inside an old one?

 

I have thought of doing that but have not done any measuring to see if it will work. Another suggestion was glue an old rag to the cap to make it look like a rag stuffed into the filler

 

'70s VW look neat if threads same

 

Gut the stant cap JB Weld it to the treaded one

 

Not sure what you mean as “modern”, but thus has the screw threads on today’s vehicles. Not too bad looking.



https://www.etsy.com/ca/listing/1678695338/vintage-chrome-locking-vented-gas-cap

 

If the diameter is the same, weld old school to new.

 

Thank you. Problem solved. I never knew they made that style filler neck in the 70’s

 

When the cap is received, post a photo of the filler neck and a photo (and part number info) of the cap, for future reference.
Thanks.

 

I'd be inclined to gut a Stant cap like 325W suggested and epoxy it to the threaded cap. I don't know if the threads match but they do sell nice shiny chrome caps with threads in either vented or non vented for Harleys. Drag Specialties is a pretty common brand seen in Harley trinket shops. I'd be packing the ugly cap along to the closest harley shop for Comparison though but those guys sometimes get their undies in a know when you mention using a "Harley part" on something else.

 

What material is the filler neck made out of? If its weld'able, Tanks, and im sure some other companies make new end pieces to use a twist cap with of varying sizes. This is the one Im using one for my '37 Buick that the stock cap fits

 

It's been mentioned but bears expansion. Modern caps are sealed. How are you going to vent your tank?
@Mr48chev offers either solution. Choose wisely.

 

I am using a modern tank that’s vented. My truck originally had the tank under the seat and now it’s under the bed. There is a vent line that goes from the tank to a canister that I have not mounted yet.

 

Over years I have vetted caps with thought ,

 

The tank has to vent one way or another to work at all. Simply put air has to get into the tank to take up the space that the gas being pumped out by the fuel pump leaves or it creates a vacuum in the tank that will stop fuel flow to the engine and can even collapse the the tank.
Traditional vented to the air though the cap works but the setup also lets the air vent back out to the atmosphere if the cap doesn't have a check valve to prevent that as many new vented caps do. Those fumes coming back out the cap are that gas smell reek that you get when you walk past cars sitting out in the sun at a rod trot at times. The air freely going through a vented cap also helps this crap gas we have now deteriorate a lot faster than gas in a sealed system. Meaning that in most cases a tank with a sealed cap and a vent hose running to a canister up front that is set up right helps slow down the breakdown of the gas.

 

I'm sure I have seen a round chrome cap in the plumbing department of the hardware store. Cost only a few bucks. Could be epoxied onto your modern looking cap. Sorry I can't give more details.

 

At one point I was thinking of taking something like this and either mounting it on my A so I could put the newer stock style cap inside it or use it to replace the stock cap. Might just be easier to attach it to the new cap as mentioned here earlier.