Bill, an entirely new headstock pin will need to be brazed in place. The original was pinned into place and brazed in at the factory in several stages, with two spigots/locating tubes in the headstem. The reason your previous repair failed was because someone welded the pin near to these and melted the bronze into the steel.
The old pin will need to be removed,and a replacement brazed into place. There is a dowel pin located horizontally. A replacement headstem may be purchased from Randy Walker.
I clean the joint and then drill thru the casting and pin front to back for a locating dowel, ( the original runs left to right), then braze the pin in.
Care must be taken whenever heating the fork, remember that the handlebar assembly is also the top triple tree, so that needs to be in place and clamped up to ensure the new pin is central, and the fork does not flex and move elsewhere.
As the casting you are brazing into is cast malleable iron, it should not be steel welded, but brazed, and care should be taken to cool it slowly, or it may crack. Make sure the guy carrying out this repair is familiar with bronze and bronze welding/brazing on antique motorcycle frames. I have only known successful repairs here with oxy-acetylene torch and bronze.
