The 7043200 is a divorced choke, large MAB model. It's going to require large main jetting. They can be completely recalibrated with small MAB's, we stock them, and the correct jets/metering rods for what you are doing.
It's going to want a lot of idle fuel as well, I'd follow recipe #3 for idle fuel.
I would also install one of our kits, to get it up to par for modern fuel, and the correct parts for the big block application.....Cliff