I still think you are afflicted by the "too much is just enough" syndrome.
Try a smaller carb(s).
Take some timing out.
And just to see where you are try to brake torque that converter. Just because it stalled at 5K behind a big block V8 does not mean it will stall at 5K behind your engine. In fact it should be less and may be about exactly what you need.
Here is another example of my "less is more" theory.
My roadster pickup truck:
2150 lbs.
300 ci six w/ 4000 stall 8" converter and 1.82 Powerglide
2.47 rear gears! (This baby hooks in a mudslide)
two tiny Autolite 2V carbs equivalent to about
370 cfm 4V flow - total
My driver shifts at 5000 (at least that's what he tells me)
About
32 deg total advance w/ flat top pistons - about 10:1 CR
Runs 11.80-90s. Best of 11.61 Built to hopefully run 10.90 w/ 4.56 gears (never tried)
