I used these petcocks on my 2 Motobecane Model 7's.
I found a brass fitting at a hardware store with the same thread on one end as the thread in the tank. I silver soldered a brass washer to the base of the thread so that when I screwed it into the tank, I could use a nylon washer to seal it. I cut the other end off the fitting, filed it flat, then tapped it internally. I cut the same thread on one end of the petcock and screwed it into the brass fitting with a nylon washer. You can add and remove washers to get the lever to line up when it is tight.
I have no reserve of course, but have had no problems with these petcocks.