If the car was a factory BB or 350 car it would also have to be an SS car, with the SS badges on it. Also, the heater hoses would be in the middle of the heater box with a BB, not next to the engine like a small-block. The special valve sounds like the RS headlight actuator? 12-bolts were used starting with the 327/275hp 4-speed cars acccording to my GM book. Sounds like you may have a 327/275hp RS 4-speed car, which were relatively rare in and of themselves. That is...if the 12-bolt is factory.