Question IS your carb a true 950 size or a 750 size bowls?
I ask this because alot of people don't realize that the 950 is actually smaller than a good 850.
a 750 size would be causing you more trouble.
I would start by enlarging the idle air bleeds and see what your air fuel is at idle i would shoot for 13.0 afr.
then restrict the idle feed to around .028 or.026 and see where you are .
my car used to run like yours and i did this and now i am 12.5 pretty much all the time cruising.
make sure you are idling on the idle circuit that is a must and most important thing.
I would also start with 84 primary main jet and 90 secondary main.
jetting affects the whole picture.
You have a A/F so you will see the improvements or not and then know which way to go.
Don't put a very low opening power valve like 4.0. run vac gauge into the car and tape to dash.See what the motor wants. I bet it would be good with a 8.5 opening point that motor needs fuel enrichment asap after you are off the T slot or transition.
measure the size of the pvcr and most likely open to min .070in
the bigger the pvcr the smaller the main jet can be the cleaner the idle will be to a point.
this is just a suggested starting point you will see real quick if the changes made are improving things,