[Alfajay]

Alex had asked: "Would an in-line resistor in the wire between the sender unit and the gauge help the situation? Just a thought ... "

Alex: It isn't a "scaling" problem. The two types of gauges (early vs late) work completely opposite. That is, the early gauges display zero pressure with the signal wire gounded (zero resistance), and maximum pressure with the signal wire open (infinite resistance). So, the early gauges show increasing pressure with increasing sender resistance.

The later gauges work the other way - displayed pressure rises as sender resistance falls.