When I ran the dual quad setup on my 32 roadster with 462" Buick engine, Carter 500's, straight linkage, fairly big cam, MSD box, it idled at 650 rpm with no problems.

Converter is a 2400 rpm B&M.

Vacuum was about 12" at idle.

Holding the brakes on in traffic took normal pressures.
In fact, on my gravel driveway the car won't start rolling until it gets a little bit of throttle.

I don't understand your two idle level comments.
Seems like you could set it to idle anywhere iin between the two figures posted.

Perhaps a little more tuning is required.

Refer to the Edelbrock manual @ http://www.edelbrock.com/automotive/eps_intro.html