Oilrag, the 261 in my pics is an April 3, 1963 casting date. The head casting date is E221 and there are no numbers stamped on the pad by the distributor, so I am almost certain this was a factory replacement engine. This engine came out of a 55 school bus. The bell housing casting date is E315 and it is probably the original in the bus.
The '54 and '57 motors I was talking about are different motors.
Joe D.
