The probe is constructed of concentric tubing (a small tube inside a larger tube). The tubes, which are separated by small insulators to keep the tubes from touching, acts as a capacitor that has one value in air (empty tank) and changes in value as the fuel level rises inside the probe. The amplifier converts these values to a signal suitable to drive a standard meter or other display device. Can be manually calibrated. See Documents tab.
6,12, or 24 inches
This probe has a standard SAE 5-hole bolt pattern, which most float type sensors have. Yes, it can be shortened down to half its length, so 17" would be no problem.
The top part of the sender above the seal has approximate height of 11/16".