Adding a longer tube is a pretty simple operation. Buy a cheap aftermarket gauge with a long tube, and cut/splice the original tube with a short section of thinwall copper tubing that's a close slip fit over the original tube. You'll need to tin the tubing with acid core solder, and immerse the new thermal bulb in a container of dry ice and alcohol to liquefy the ether while doing the splice. That drops the temperature of the bulb WAY below zero and prevents the ether from evaporating while you make the solder splice near the gauge head.
Jerry

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