I will soon be ordering a new Temperature Gauge with sending unit for installation in my '49 GMC 3/4 ton dash gauge cluster. The engine in my '49 GMC is a '54 Chevy 235. Will the temperature sending unit that comes with the new '49 GMC temperature gauge match the size of the sending unit in the head of the '54 Chevy 235?
It should. At some point, I believe '55, Chevy enlarged the hole in the head for the temp sender. They require the bushing that Chevy Duty sells to adapt the truck sender to the hole. As far as I know, the '54 still has the small hole, so you should be fine.