Thanks for great advices, I really appreciate them.
The cam is 272/278 @ 0.050, 0.708 lift and Crane states that it is a "oval track" profile whatever that means. Heads are ported Merlin iron rectports, big Dart single plane manifold and a 1050 Dominator. Headers are quite big, 2.375", so that might cost some torque. 12.4:1 compression (measured). I think 650 ft-lbs @ 5000 and 750hp @ 6500 is quite close. I use 50% Sunoco GT 104+ and 50% Shell V-power as fuel.
So get the car to the eights, I will try to:
1) Install the chute. I have to remove the body from the car to do this and relocate the fuel cell so it'll take time and people. And beer.
2) More gear and rpms. 4.29 or 4.33. 4.56 is too much if I want to stay below 7000. I believe I'll do this during the long and dark Finnish winter.
3) Try the ballast. It's cheap and easy to do and I can try it this summer. Should help also in the slippery airfield-tracks we have.
4) Aluminum heads to reduce nose weight if I can find the money. AFR 335 CNC's would be the dream.