Your fuel gauge sender problem peaked my curiosity. I have a similar problem with mine, but at least the part number is stamped on mine, though I can't get the d...mn thing out of the tank! I usually try and clean the surface of the rheostat which works for a while.
I searched on AC 2 litre and found the following two sources of information, the later being useful for all AC models. They were
www.ac2litre.com which gave me the link to
www.holden.co.uk.
I then searched on the holden site for "fuel tank sender". Some of the items have a video explanation basic principles of how they work
e.g.
https://www.holden.co.uk/p/sender_for_original_moving_coil_gauges_two_terminal_ , sender for an XK140. Didn't look for one for your AC but maybe you can do an occular comparision or give them a call? They also listed a device to match sender to gauge.
Hope this helps.
/Paho