I hope the information on my site (mentioned above) is helpful to your members. Two quick comments regarding the problem identified.

First Edelbrock carbs are very susceptible to high fuel pressures. Make sure to keep the fuel pressure below 5 psi, volume is much more important that pressure.

Secondly it does really depend on your total engine configuration, but in general you will find better drivability with a 4 hole spacer on any dual plane manifold. An open spacer concentrates the intake revision and associated turbulence right at the carb base which can effect mixture distribution, velocity, and proper flow.
Whereas a 4 hole spacer maintains the airflow integrity. I would definitely try removing the spacer and seeing if there is a noticeable change.

Volvord 784VC
http://www.telusplanet.net/public/gilesij/Volvord/