Currently working on a 650vac sec carb on a 340.Good low speed response but little lacking on high end 650 dbl pumpers are just about perfect on a street 340 I have several and overall hard to beat over all. I like a 750 on a light car the 650 on heavier. I have just built another 800 dbl pumper and its great on high end and ok at low speed due to the 4.56 gears on my 340 Duster. I have not track tested it to see what the 60fts and 330 are like, your combo a 650 dbl pumper might be a little small but it will out perform most any other carb