Moss went to some effort in 2011 to improve the quality of this unit, and they sent me one of the new ones for my consideration. It now works well electrically. Unfortunately this unit now (or still) has the wrong range of mechanical motion, and the wrong range of electrical resistance.

Assume your car gets 25-mpg for 300 miles with 12 gallons of fuel. If this sender unit is installed as received, you can expect the gauge to read Full (or pegged past the "F" mark) until the fuel level gets down to about half tank (150 miles). Between half tank and quarter tank it would go from F to 3/4 on the gauge (75 miles). Then it would go from 3/4 reading to sucking air at 1/4 reading (75 miles), never reading less than 1/4.

Some improvement in gauge reading might be gained by extending and/or bending the arm and by recalibrating the gauge, but it will most likely never be capable of displaying correct fuel level. It is also my conviction that we should not bastardize a perfectly good original part (the fuel gauge) to accommodate a faulty replacement part (the sender unit).

Two years on (November 2013) Moss is still selling this one as-is, knowing full well it does not work properly. If you buy one of these, and you actually figure out how to use it, please let me know how you did it. For a full report on how it works (or doesn't work), and explanation of the drawing, see article FG-115 in the electrical section.

Addendum, August 9, 2014:
Scarborough Faire fuel level sender unit also faulty.

On 05 August 2014, Dominic Clancy in Switzerland wrote:
"The new tank sender is attractively priced, and looks the part with a twin contact along the spool. The problem? The resistance is only from 0 to 18 Ohm, so the fuel gauge is never going to work correctly with it, it is so far out of spec from the 0 - 70 Ohm of the original".

Scarborough Faire fuel sender unit with wrong resistance range.