stock filler location

[SS Tim]

Sounds like you are missing the intent of my post.
I do not have a flush cab mount filler.
What I was trying to point out is that GM mounted the filler directly to the tank inside the passenger compartment. Also the need for and undesireability of an inside cab connection to the tank. If you must, consider a filler check ball like most late model tanks have at the tank to prevent back flow.
The last year I remember a "connection" inside a vehicle was the 68 down Camaro. Both the Suburban and Blazer had fill tubes running through the passenger compartment but again were solid from cap to exit of the compartment as is my IH pickup.