An Edelbrock Performer will give you a big performance gain over the two barrel Rochester. A Holley 600 C.F.M. carb would also be excellent. I also like center-mount float's and vacuum sec and a electric choke, secondary metering block's with jet's make tuning a snap on the holley, good luck on the Old's I used to own a 74 with a Rocket 350 . It was a pretty torquey car.