why don't you use the sender from the engine it "worked" with? maybe your sender doesn't have a good ground, like if you used a sealant on the threads, or teflon tape
the position of the needle when the key is off is the no voltage "resting place", as the resistance of the sender changes, it goes up, you might be able to [carefully] bend it but then what would "normal" be, or "hot"?
all the temp gauges on these ol trucks are simple approximations - use a good thermometer to check the water in the rad to see what the gauge is telling you, and go with that
Bill
