Thanks Bruce for the mention.
As all things Brougham, it is different than the standard fuel tank. The standard 57 tank has the depressions on the top, but the holes are not pierced for the Brougham low fuel tell tale sender, fuel gauge sender, or electric fuel pump.
The module Bruce speaks of is for the Brougham fuel sending unit as it has a different electrical circuit than the regular Cadillac. This electronic module allows the use of standard Stewart Warner sending unit which will drive the Brougham fuel gage and light the low fuel lamp.
The Brougham had its own Master Parts List and none of Brougham parts show up in the regular Cadillac Master Parts List.
I am in the process of getting a box made to hold the circuit board to complete the module project. A different version of this module will replace the goofy oil sending unit that worked the same way.
David