The last 440 bracket motor I used a set in like to be shifted at or under 6000 RPM, it was a TRW 11.5 to one motor with ported 906 heads, solid roller cam and lifters, TM7 inatke and so on. It seem to run into a wall about then. Other similar 440 bracket motors with LY rods would stop pulling hard around 6400 RPM I would take the car to the track and try shifting it at 5000 RPM for two or three runs and then try 5500 RPM and then 6000 RPM, keep raising the shift RPM until the car starts to slow down (look very closely at the 330 and the 660 ET and MPH times ) and then go down 100 RPM at at time until you find the sweet spot