Which Branine Chevrolet was your car sold new at? There was Don Branine Chevy Olds, Winfield Ks and then Branine Chevrolet, Mulvane Ks. The two dealerships were the same family and about 30 miles apart. I think they were both involved with the hi performance cars. Did you have any luck with the Kansas DMV title history?
The guy listed on the plaque (Allen Patterson) is a well known racer/engine builder in the area. He might be of help.
http://www.patterson-elite.com/