Oddly enough, a web search for GM# 1510774 came back with an actual result.
If you want to use that NOS GMC Temp Gauge, click
HERE. The source in Holland says they have 2 in stock (looks like left over WWII parts stock) and the pictured sending unit with original GMC box looks like the critter you seek. Be ready to pony up for the asking price plus international shipping though.
