Big Block Tunnel Ram 660s Questions

I am using a MSD pro billet ready to run. 18⁰ at idle and 38⁰ all in about 2000, 2300 IIRC. I am using vacuum advance and due to the 660 no having ported vacuum available, it is hooked to manifold vacuum.
Is the vacuum advance adjustable? You may have one of the rare instances where ditching the vacuum advance is advisable.