Doing some cleaning around here and I am probably going to tear this F engine down into parts but it would be nice to know if anyone can help with the serial number. The number on the block is F 238589. I got an SD40 large window carburetor with the engine (but not installed) that is date stamped 7/11/66 so I'm not sure it is the original carb. This serial number pre-dates SOR's serial number chart on the website so if anyone has any way of providing additional info that would be great, thanks.