[Rory McNeil]

Also, the 3310 & 3310-1 have the replaceable secondary jet blocks and are rated at 780, the later (& cheaper versions) 3310-2,3,4 etc use the secondary metering plate and 750 rating. I believe that the later 750 versions also use the Holley manual choke setup, while the 3310 &-1`s that I have owned, always had an automatic choke. Also some of the later carbs used cheap plastic accelerator pump arms, secondary diagpram housings, and manual choke units.