adjusting holley floats on shaky engine?

Either "rig" an electric pump so you can set them engine off, or just set them as you would any other carb, IE by measurement. I don't remember, anymore, what this is for the various float bowl configurations, but I'd bet it's on the Holley website tech pages.

If you use an electric pump, remember that pump pressure DOES affect level, so you'll have to figure a way to emulate your running pressure.