I not long ago had to swap out the old XF tank for XG, this is a per curser to a EFI swap later on. Also I had to get it in before the space cab mod, as it will not be removable afterwards.
I did have the problem of over pressurization, was a bit weird to see the amount of fuel that can be forced through the main jets, lol..
This is how I have overcome the problem, for the time it takes to fit the EFI motor & front loom..
Fuel regulator is set to 3.5psi, return line feeds excess back to the tank