That would be my brother Florida_70Bee.

Ran a best of 13.47 the last time we were at Gainesville with a 1970 Super Bee 383 automatic.You would need to ask him about the combo.

I have a 69 RR 6 pack stroker 4 speed dana 410 same issues and almost identical times first time out, look at:

Fuel delivery
Headers
the heads themselves

stroker might be a bit different since it needs more air but the combo is close. The MPH should be over 100 minimum IMO for a six pack car.