Do you have the transition slot set on the primary and secondary?
.020 square up front and barely visible in the back. You need to set the idle mixture biased to the front. The idle circuit is what you drive on in a street car to approx 2500 rpm. You will have to lean that circuit with larger idle air bleeds, smaller IFR, or both. IMO with 13" at idle the holes in the butterflies drilled by the PO are not needed. You may want to replace them or close them up with solder or rivets.
I run a 66 IAB front and back with a .028 IFR. Front 7/8 turns, rear 5/8 turn. 12.8 AFR idle in nuetral and 13.5 ish light cruise till the primary jet comes in at 2500 with a 3.91 gear.
