The internal works of all the gauges from 48 to 55 , and possibly 56 , less the faces - are the same. The gauges are assembled in about three layers - a mounting plate on the back of a round gauge body, then a face. The mounting brackets are generally the same but sometimes need to be flip flopped to be mounted in the cluster of another vehicle. in the 51-52 they are diagonally mounted. Possibly horizontal or vertical in 48- 50.
Sending units are the critical part (for the 56 12V equation) -matched to the gauges (all the same/interchangeable from 48-55 per instrument I think - Number Dummy can confirm or deny) and they are the same for both instruments and idiot lights 48-55 - that's confirmed.
So, you could take a 53 temp gauge and sending unit and install it on your 50 by just changing the face, and installing the original mounting plate on the back and it will be ok. Of course there are exceptions which I'm sure folks will throw in here. We can address those as they come up.
OBTW did you know that modern mecahnical and electric gauge works can be inserted into the older gauge bodies and used? My oil pressure and temp are modern mechanical gauges, mounted in the original cases with the original faces and mounted in my stock gauge cluster on my 51 F1. You'd never know th ediff, except the temp gauge reads accurate temp when th eignition is switched off instead of going up to "H" as a stock electric gauge would.