[RustyYellow]

I'll take a crack with this Guido. This is just a general thought of why carbs are different, and years or where sold is only examples.

One carb, may of come off a late '68 tractor that went to a dealer in Georgia where the altitude is only 60' above sea level. One tractor, but late '69 went to the mountains of Colorado where the altitude was 6500' above sea level.

The third tractor, but a 1972 year went to Minnesota.

All same size engine, but possible different EPA regulations, engineer update changes for the year(s) to work for given area, while being the same cast carb number.

Factories don't throw away parts. They use up what they have and many times it's a mis-mash of years, but it works.

I know I couldn't give you a definitive answer on the needle seats as I don't know without having the carbs in hand to compare these areas, but since there's 2 different rebuild kits, there's enough difference somewhere, to have a need.

That need, according to that carb's serial number could of been an update of improved seals due to fuel or heat that the engineers determined was needed for that time, but we'll never know as there's no one to ask --- why.

Del