Well that was both easier and harder than I thought it would be.
Built the firing pin from a drill bit. Not owing a lathe, I used a drill and file to turn down the the shaft for the pin. After that I used a dremel tool and a chainsaw sharpening bit to grind the radius required at the rear of the pin (facing the hammer).
Then came the careful and repeated measurements to set firing pin protrusion and overall length.
Finally I heated treated in a very imprecise manner (really a shot in the dark) and installed.
Tested it yesterday and rifle performed as it should and hopefully the pin will continue to function for years to come.