EFI fuel tank in C-10 question

[86LT1C10]

I am thinking about putting in a rear mounted tank in my 86 C-10. I am needing it to be baffled for an in tank electric pump. I have seen many using the Blazer fuel tanks. Now, I have seen some with the filler in the passenger side and some on the drivers side so some of them have been installed backwards. Do they still work backwards? The main reason I ask this is that I am thinking of using a tank from a 97 Tahoe and mounting it sideways so that the filler is to the rear so that the filler is behind the licence plate. If a tank work backwards then one should work sideways???? Unless one of you has a better idea of an OEM style GM fuel tank to use that has has baffles and exits to the rear and wont cost boocoos of $$$$'s to buy.