I tend to prefer double pumpers fro a couple reasons.
#1. One less theory to rely on. When you push down the secondaries will always be there because they are "mechanical"
#2. If your carb size is not 100% correct you don't have to change spring sizes in the vacuum diaphram to get them in sinc. I also like having that second set of squiters to get me going
The only reason I would go with vacuum secondaries would be for gas mileage & I don't see that being a big factor in this type of car.
All of the above are, of course, my opinion & some will of course see the subject quite differently
