Perhaps someone can measure their sender but if the twelve is like most Packards, unless the sender is already out of the car that is quite a project.
Motor Manual, Eleventh edition, says the twelve used Moto Meter gauges and another source says Stewart-Warner and Atwater-Kent is also a possibility. All used a straight resistance type sender -- unlike some gauges which used heater and bimetal type senders. Cannot say on the MM but if S-W, I suspect it will be the same obsolete range that was used on some models thru 1947 -- 100 ohms empty, 0 ohms full. If that is the case, the modern sender that is closest is the GM unit of 0 empty and 90 ohms full. While you can reverse the unit so 0 is at the full end, that one will not work because the gauge never drops below approx 1/8 of a tank.
Modern resistance ranges for various brands are quite different so finding an aftermarket or universal sender in that old range that will adapt to the tank is all but futile. If the company you mention will custom make a sender that is a different story. If that is the case would appreciate more details on the company as others could be in the same fix.
There is one company that does advertise custom making senders for the old gauges and they would probably know the range for your car. No idea if they would share unless you buy their sender but maybe worth an inquiry.
http://www.mykmlifestyle.com/KM_Lifestyle_Fuel_Senders.html If all else fails and the gauge portion is working you could buy some fixed resistors or a 1 or 2 watt linear potentiometer of around 150 ohms off ebay and get a fair idea of the range. Hook the resistance up between the sender wire and ground and then adjust until the gauge reads empty and full. Measure the two points. There is a slight chance the ohm range could be higher than 100 -- the modern high end S-W range is over 200 ohms -- but don't think they went that high in those early years.
This Post was from: https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=175384