Finetuning questions - do I need a high-stall torque converter ?

BINGO!

The Ignition Timing Curve was the issue.
I have a MSD 8388 Distributor - which I bolted on originally with initial settings.
I did not have a clue that the curve would make that much difference.
Initial timing is now around 10 degrees - max 34 degrees.
Have first tried one light blue and one silver light spring - with the blue stop bushing.
This was already a big improvement.
Then I went to the 2 silver light springs - which gave the most improvement - still with the blue stop bushing (21 degree total advance range)
See curves sheet in attachment.

I checked carefully for pinging - and had to turn from 36 to 34 degrees max as it tended slightly to ping in transition from cruise to WOT.

Now it spins the wheels at free will :iconbigg:

As next step I was able to borrow a Holley 4160 600cfm vacuum secondary for testing.
I will recondition it first and then tune it to my engine.

I was able to buy a Holley 4667-2 600cfm double pumper for around 120 USD which I will recondition as well - then I can compare which carb suits me best.

Thanks again to all for you great help! Will let you know the outcome from the next quarter mile passes next year....