John,
On the 1954 Suburban, the fuel line is part of the sending unit. I think that the Chevy Duty sending unit to which you refer is for a pickup gas tank (which is in the cab, behind the seat). I am almost certain that the 1953 Suburban sending unit is the same (just like the diagram in Sect. 8, Sheet 1).
Your tank might have been "adapted" at some time - most likely because the sending unit had to be replaced and no one sells a new replacement.
The anti-squeak between the tank and the support bars above the tank (not between the strap and the tank) looks like a thick roofing "tar-paper". I used strips of black vinyl but 3-4 layers of 30# roofing felt would do fine.
Tim
