Hy beltfed and guys, on the older GM stuff like the water temperature senders used the same ohms range as the fuel tank senders 0-30 ohms, one tester could test the fuel gauge sender and the water temperature sender. Oil pressure senders were a bit trickier you had to know the maximum reading of the gauge in p.s.i. as one of the criteria for ordering the correct sender. As usual all the manufacturers used different ohms ranges for their oil gauges and senders and the aftermarket used their own as well Stewart-Warner used their own ohms range as well. So you had to use the correct sender for the gauge you wanted to use, not so hard to do when our trucks were relatively new, but now half a century later senders for our original gauges are no longer in stock unless 54 3600 could possibly find n.o.s. ones if we furnished him the part numbers. Classic Instruments website has some ohms ranges for the different fuel gauge senders they sell, have a look and you'll see what I mean about everyone being different, hope that helps.
