Intake and carb choice

Glad to hear your not giving up on the tunnel ram.
I bought a rpm not long after they first came out new due to all the great
magazine reveiws. I was very disappointed myself and sold it.
It is hard to go to a dual plane manifold after running a single plane
or a tunnel ram and be happy with the results.
If your Holley's are not tunnel ram specific like the 660 center squirters...
For example 1850 600s each carb is designed with idle restrictions sized for
using carb as a single. So you have twice the needed fuel at idle pairing them up
on a tunnel ram. You can tune these restrictions down to what your engine needs with a piece of wire to slow down the amount of fuel that can pass thru the restriction. You may have to experiment a bit to find out what size wire is needed to make your engine happy at idle.