I have the same problem with my 69 Swinger. Saw this on an earlier FABO thread on this same topic a few months ago. Have not purchased/tried it yet, not sure I understand how it is installed.
It appears that it fits in snuggly with your filler tube where the gas cap is, reducing the diameter there to properly fit a modern pump. I’d be interested to see if that works, as it’s significantly cheaper than getting the tube recored to fit
