Having not built a Kitfox, I have no familiarity with this particular valve. However, since a very large number of homebuilt accidents are fuel system related, I would think carefully about using a valve of unknown quality from a store like Harbor Freight. I certainly buy stuff there, but usually stuff that has no cutting edges, moving parts, etc.
(my electric fly-swatter comes to mind). I remember a set of wrenches that wouldn't even fit the intended size of bolt. If these crappy Chinese factories can't even make a 1/2 inch wrench, can they be trusted to make a critical component like a fuel valve? I would suggest at least finding a high quality American made valve, if not an aviation-specific part.