I sold a nice rebuilt one last year to a Cdn Poncho member - It was casting # 3736567.  I'd bought it years earlier for my 57 Chevy 235. It had the single heater hose outlet on it for non-heated manifold.  I believe it was correct for 55 - 63 235 & 261.  

I think the member buyer put it on his early 60's car.