Fuel Tank Conversion

[69 GMC LWB Pickup]

I have just converted my 69 GMC LWB P/U Fuel tank from the cab to under the bed and now I am looking for the right fuel neck and fuel door to put into the bed. I have searched the web to find all kinds of fuel doors but, they are all for newer cars and trucks. I would like to find one that is specific for this application. I have included a photo of the wood bed and the fuel tank. I wish to put the fuel door and neck through one of the wood planks. Can anyone tell me where I can find a fuel door and neck? Would like to find something chrome and with a lock.