You just might have gotten very lucky there. The engine MIGHT be a 261. It's got a PCV ventilating system, and the valve cover appears to be from a much newer truck than it was in when that picture was taken. The picture isn't clear enough to see if there are captain's bars or big oil filter ports, but the valve covers with the oil fill in the center were mostly on mid to late 1950s engines. I can't remember seeing that type of plug in a 235 valve cover. The big vacuum fitting on the intake also screams "BIG TRUCK ENGINE".
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!