Ok, now it looks like time for Plan B:
It might be easier to substitute a valve made for a different engine. Back when I worked in the parts business I did this a few times on my own projects with entirely satisfactory results.
Obviously critical dimensions are head diameter, stem diameter, overall length, and (sometimes) face angle. You can grind down a valve head that is slightly oversize or off by a degree or two. Keeper grooves can sometimes be a worse problem. You can often substitute a valve with the "wrong" grooves as long as you can get the keepers and retainer that belong to the valve you are using. Normally, an exhaust valve can be used to replace an intake, but not necessarily the reverse.
Start here, and happy hunting!
http://www.mellingengine.com/Portals...%20291-293.pdf
Ray