Now that's interesting and thanks for posting the pictures. It appears the original cap was used and the ' unit ' also has an electrical sending ability to a gauge somewhere ? I have never seen anything like that before. Brian
I never saw that system in real. Absolutely, the original cap is drilled to put the system. I don't know if it's an electrical sending, all pictures I saw don't show electrical wire connected on it. I think it's a mechanical float and the little rod at the center, up and down in function of fluid brake level inside the bowl, to make a quick check inside the engine bay... But I'm not sure ! We saw that system in France until 1966, next it disappeared.
Franck