Alden - this link to our website will help explain the casting numbers:

http://www.thecarburetorshop.com/Carburetor_ID.htm#IDRochester

Jon.


Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop