Good day,

Newbie here, and getting familiar with my new-to-me 1970 Series IIa ambulance. With the pair of underseat fuel tanks, is the fuel gauge supposed to show the level for the tank that is selected by the fuel tank cut-over switch? I can't test this at the moment, as both of the sender float arms do not seem to move/swing in the tanks, which I assume they are supposed to do.

I believe so , you will get more info if you use the search feature too
If you remove the wire from each sender it should show full on the gauge