Carburetor for 640

[NGaMountains]

I just bought a 1955 640. The I and T shop manual says that the Marvel Schebler carb was used on gasoline engines while the Zenith was used on LP gas version. I have the gasoline version and yet I have a Zenith carb. It has a float and pintle valve in it. Is the book wrong? Were there some Zenith gasoline carbs used on rhe 600?

 

[old]

Zenith is a replacement for the M/S carb it had when new

 

[Sean in PA]

I believe that all of the hundred series gas engine tractors came from the factory with a M-S carb, but at some point after they stopped making the hundred series, Ford started specifying Zenith carbs as replacements. Same thing happened to the '65-'75 3 cylinder gassers, which all left the factory with Holley carbs, but at some point Ford's spec for replacements for those became Zenith carbs as well.

 

[NGaMountains]

I am guessing that this carb was put on the tractor later, then. Since it is a 1955 model it no doubt had the M-S carb originally