Front suspension has got to be right before worrying about rear suspension. What is it besides the QA-1s?
A Chevelle at 3000 lbs., is pretty cut up so 50/50 should be doable.
That said, my 3880 lb. Chevelle was 59% front/41% rear and ran in the 9's launching wheels up every pass.
What is the rear suspension is in it now? Footbrake or transbrake launching?
Some preload on the right rear is required, which will put more weight on the left front.
Make all adjustements with you in the seat.