The original Jup is on the right and does not have an arc on the facia and also is fixed by two tabs welded to case.
The water temp has similar inards to the more modern ones. So a working one was chosen and the facia swapped and the needle was painted.
Care is needed removing the facia on the water gauge as the needle cannot be pulled off. it needs to be bent and the facia slid out.
Replacement is also difficult as you need to align the needle on its shaft with the stop post. There is a tab on the facia surround that locates in a slot to register the position.
You then need to carefully bend the needle to get it to touch the stop post and not foul the aperture sides.
It might be possible to use some tweezers through the light window by rotating the transparent cylinder (but I just thought of that!).
The facia can be removed by turning the bezel a few degrees.
Note the soldered end which we can use to refill.
The oil temp has no replacement as there are few with an oil temp and oil pressure gauge combined. So the capillary has to be renewed and refilled.
The bulb can have either a female or male nut check which your rad or sump has.
The capillary tube is 2000mm long .
The procedure for refilling follows.
Obtain ether and freezer spray.