Didn't NAPCO do 4X4 conversions on trucks other than GM? You might want to expand your search for that steering knuckle to trucks other than Chevy. Chances are that some Ford, Dodge, and possibly International 4X4 conversions might have used the same front axle assembly.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!