You might want to do a bit more troubleshooting first, before dropping the tank!

Disconnect the plug to the sending unit at the frame rail, and jumper it straight to a good ground... Does the gauge now read empty? If it still reads full, the problem is the wiring or the gauge. If it now reads empty, it could still be the tank ground, not the sending unit.

If you're sure it's the sender, pm me again, and I'll get it in the mail.

--Randy