? about which fuel level guage to use.

[Streetmaster]

Hey yall, got a ? about an Autometer fuel level guage, for my 76 GMC pu. So far i have a volt, water, oil pressure guage from Autometer in my dash. Now im trying to figure out which of the two fuel level guages Autometer has for my pu to use. They are both the traditional chrome style guages. One is part (#2514) with a range of (0) Ohm's empty to (90) Ohm's full, the other is part (#2518) with a range of (16) Ohm's empty to (158) Ohm's full. My pu has a stock fuel tank, and a stock float in it, which i dont have any idea what the range of Ohm's would be on my stock float and sender unit. So if anyone would have some idea of what it would be (Please Advise) ThanX