Sent you a PM on the same question asked in the message.
There should be a 'pink' colored wire that the sending unit plugs into and it is part of the wiring harness for the tail lights.
The pink wire goes to another plug under the dash by the parking brake pedal and continues onto the gauge in the speedometer which is also pink in color.
Keith, I am gathering everything I need to upgrade parts for my 20 gallon tank. I was wondering the same thing about that sending unit pink wire. I have not dropped the tank yet because I am waiting on replacement parts. I am however, trying to trace all the related wires and connections. On mine, I DO NOT see that lead wire thats in your image with the connector plug. I found the ground to frame but confused on the pink one.
Under the dash, I traced the pink wire from gauge to a connector plug that has like 8-9 wires on it where you stated, by the brake pedal. The pink is on one end of that plug. From that connector moving forward, it goes somewhere just above the fuse box. On the engine side I see it running directly to the solenoid and it has a 30 amp fuse on that line. Seems odd or maybe it is the wrong trace?
At this point (the connector plug under dash), does it run straight to sending unit or to another connector plug of some sort? Something is throwing me off. What I am missing or looking for?
Also, when I receive the new sending unit, can I connect it without putting it in the tank so as to test the gauge? I know I would have to ground it at this time too.
Also, what size are those three hoses at top and how LONG are they? I just want to get everything ready for the drop. Thanks