It's possible to repair those temp gauges by splicing on a cap tube from an aftermarket gauge. You'll need a short piece of copper tube that's a slip fit over the nub that's left on the gauge head, and an aftermarket temp gauge to scavenge the cap tube from. The trick is keeping the fluid inside the bulb while you're doing the soldering.
Get a plastic container like a Tupperware bowl and put several chunks of dry ice in it and fill it with alcohol. Immerse the sensing bulb and as much of the tube as possible in the cold liquid. This will condense the vapors and hold them in suspension while the tube is cut off, filed square, and soldered into the splice tube. Solder the splice tube onto the original gauge head first, since there's no need to keep anything cold on that end. Use a micro-torch or a BIG electric soldering iron, and acid core solder to make the repair.
Jerry
