this is how you limit the mech adv on a HEi to allow more initial at idle.
you can do it yourself.
do that first.
If the IAB's need fine tuning I do it by soldering up a spare IAB and drilling to 1/16th" .062" Then using a AFR gauge I file/hone the air bleed size a bit at a time by hand with the drill bit to open it up leaning the circuit. Test at idle and just off idle for smooth response and acepable AFR.
Very small change makes a big difference.
The AFR gauge will not read at idle with open exhaust.
I looked up the cam but there is some confusion on what cam you actually got there. The cam specs don;t match the cam grind number.
You may have the bigger TFS cam. Thats what your motor is acting like.
measure the lobe lift. Measure the manifold vacuum at 1000rpm idle speed.
(indicates the cam size) give it all the initial base timing it wants at idle.