Double pumper with automatic

It all depends on your combination. I used to run a 750 vacuum on a 383 with a single plane, 727, a high stall converter and 3.91 gears. I had a huge off idle stumble when you mashed it to the floor, even with a 4 hole spacer. I finally decided it was telling me "more gas stupid" after playing with timing and other things so I swapped the vacuum unit for a 750 DP'er and guess what, problem went away. Now you can come off idle and fry the tires off her with narry a stumble all the way to 6500 RPM and over 100.
Basically if it's working out for ya leave it alone but for minor tweaks.

Terry