This may be lengthy but may help someone. Have a 1947 long-door coupe. Installed new Bob Drake gas tank. Fit very well re size, shape and features of the OE tank EXCEPT the hole and steel collar for the tank sending unit is too small to use an OE sender unit
. It's set-up to use their 12 volt sending unit. My car was previously converted to 12 volt and dash gauges had 12 to 6 volt reducers. My OE Ford sender unit worked fine and was very accurate. Their resistance-type 12 volt sender did not work correctly with my dash gauge.
Although the my OE sender's mounting screw holes matched their outer set and I could lower the OE sender arm and float into their tank, the bottom of my OE sender had to be about 3/8 inch above their collar hole. They correctly cautioned not to cut their collar hole larger because leakage could occur.
I figured a rather simple solution for myself. At hardware store bought a rubber gasket that goes between the toilet tank and toilet base - has a beveled edge on one side and typically they are all the same diameter. With a sharp knife I carefully trimmed the beveled edge off. This gave me the extra 3/8 inch of height I needed to attach the OE sender unit to tank collar. Using the thin rubber gasket they provided as a guide, I drilled holes thru the new 3/8 inch gasket for the attaching screws. Bought longer attaching screws (#10-32 x 3/4") .... Note that the screw holes in their tank collar are "dead-ended" to prevent leakage, so one must buy a specific screw length.
Installed the sender unit using Permatex Ultra Blue sealant (gas resistant) and grounded sender to frame. Sender and gauge work fine
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