Which currently available vacum heater valve works on the 420G?

Saloons
1

I see several on Ebay. XJ, XJS, and a few more. I have one on another car, but don´t know which one it is

2

Solved it.
The one I have in one G is from the XJS 1976-83, and it works, provided it´ s mounted in one of two possible ways.