Your timing is not locked out. You do not need or want a timing curve.
You want full fixed timing 36deg at idle and 36deg at rpm.
Eliminate the timing curve. This cam need fixed locked timing to get a clean launch.
Then remove the carb spacers. Mount the 750 carbs direct on the intake manifold.
This is where you start tuning..
before you reported good "drivability and throttle response . Now the story has changed. WHY?