Hi Alvin,
Dont think it would have been carby setup as there would be no need for a return tube (only one tube required).
My guess is the builder intended to use an external pump. It looks like the service hatch is too small to fit a pump through, hence the external theory.
You could use rubber stoppers instead of the hose. Or grind the tubes off and weld over the holes {(If you can find anybody crazy enough to weld a peterol tank) dont try this at home kids}.
Not sure what Peter means about not having two pipe arrangement (sorry Peter, not picking on you
) I thought all EFI engines had two pipes one for tank to EFI and one for EFI to tank.
If I remember I will post a pic of my tank tomorrow night.