Most of my 440 combo's which have been fairly mild (under 11:1, hydraulic flat tappet cams in the .530ish range and steel heads reworked) I always shifted at 6,000. My current engine is still mild by most standards, 10:9:1 with TF 240 heads and a .557 solid cam. If I'm running 1/8th mile I shift at 6,000, but if I run 1/4 mile I shift at 6500. Doesn't seem to make a difference, but with the gearing and tire size it seems to be more consistent in the 1/4 if I shift at 6500.