650 DP or 750 Vac secondaries? Which one?

While I was only bracket racing years ago, I swapped between a 650 DP and 750 vacuum and, as noted, there was very little, if any difference at the drag strip. Switching to a 750 DP picked me up about a tenth on my particular combo over the other two. Can't say if I got each one "optimized", but they were all extensively tinkered with - jets, squirters, pump cams. I still tinker because any change to the car and engine can change the carb "tune-up".

A double pumper will launch the car harder IF you can get it tuned right. In my opinion, it is usually harder to tune a double pumper than a vacuum carb, especially if you don't have a lot of gear and converter. I don't think you do. So, in my opinion, the 750 vacuum should be an overall better performer with the vacuum secondaries.

With the 650, you can always test & tune at the track when you have the time, money and tuning parts.