Ian,
I used aftermarket valves for a IHC farm tractor/crawler engine. The valves were manufactured by Sealed Power (now a division of Federal Mogul), and from the receipt the part numbers were V843 and V1542. The part numbers are still listed in their eCatalog, but there are no dimensions. Originally the selection was made from a hard copy catalog at my favorite engine shop, that would have listed valves by primary dimensions and would have been how I determined they would be suitable. It does mention online the engine was in use in a series of about four dozen engines from 1953 to 1968.
As I recall (circa 1987), all I did was shorten the valve stems and cut a new retainer grove. I do remember the stem was quite hard! I am surprised that I do not have a sketch for it in my F28's file, but all I could find was the receipt.
the eCatalogs can be found here:
http://fme-cat.com/and the search page for the Commercial/Agricultural applications here:
http://fme-cat.com/Commercial.aspx(It will also find it under the car and light truck search.)
-Doug
