Hmm, maybe the picture will explain it better.
The grey valve encloure on the left is not deep enough to fit the radiator valve in a horizontal position.
Since I can't locate a straight radiator valve, my plan is to sweat a cast 90 onto the stub, then a union and the regular valve.
It's a regular gate valve in the pic, and unless someone has a reason not to do that, or a better alternative, that is tomorrow morning's project! Phil