Spectra fuel sending unit

Has anyone had luck with a spectra fuel sending unit .the sending unit i have in the car goes to full then drops like a rock to empty after a few miles on my 66 Dart .Thanks
Do you still have the OEM unit? If so, get it rebuilt by Instrument Specialties, Inc., N. Kingstown, RI 02852.
They are the best in the industry, had mine done by them. Very nice work.