The "sender" on your original-equipment gauge is actually a small-diameter tube filled with a liquid similar to Freon that expands when heated. No, it doesn't come apart. It's a professional restorer's job to rebuild that type of gsuge. I'd suggest an aftermarket gauge, either direct-reading or electric, unless you're doing a restoration of the truck. Getting an original gauge rehabbed is pretty pricey.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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