Ok, thanks: there are enough heads and variations out there that I have problems remembering them all. The heads should not be the problem. We have Edelbrocks with similar flows, and very close to the same SCR/DCR and with 3.55 rear gears and a 2500 stall TC, it will spin the tires pretty good. (We have actually not yet floored it from a dead stop in 1000 miles LOL, but 1/2 or 2/3 throttle with a little turn on the steering wheel and it will spin and set the car sideways immediately.)
I will tell one story that might help give some perspective. I had a 1970 Ranchero with a well built 351C, with a bit over 10:1 SCR, low 8's DCR, and a low duration, high lift cam that was a great torque engine. I always estimated it at around 350-375 ft lbs torque and around 325 or a bit more HP. It had a 3.08 rear gear and stock TC, with the stall speed probably below 2000 RPM. It would spin the tires some but was not a tire burner. It would always beat stock 440 Mopars in street drag races but in looking back after having several rally and other cars, it was not a great machine off the line. It figured that the low rear gear and stock TC loaded down the engine at a lower than optimum RPM. Once it got rolling just a bit, it took off great.
I tend to think that you have a similar situation with your 2.94 gear and 2000 RPM TC. It is just never going to take off like a rocket. Your engine is just not up on the torque curve when the TC starts to lock up. I am willing to bet that you can tune the ignition and cam timing all over the place and it won't change things much at take off. I know this has been said before, but I hope my above similar build helps with perspective. If you had a manual transmission, you could just rev the engine more and slip the clutch as you took off and it would be all better.
IMHO, the exhaust is likely just going to hurt the top end RPM range. When I went from headers to standard exhaust manifolds on the above 351C engine, the top end suffered the most. It is not great, but I think that any exhaust reversion is a minor factor and is not huge at 2000 RPM; your cam is not all that radical.
