The manifold mods for the 6 pack are different than the mods for the 4 bbl. You will have to choose which you want to use or compromise. I have another of these set up for the 6 pack. I have always run it on my 6 pack Challenger. It likes RPM's. It likes the 4 speed and it does not like idling. Last time I had it out running, it was with a 11:1 440. The cam was the DC 590 lift. I idled the motor at 1000 to 1200 rpm. I ran a 4:88 gear with a 27 inch tire. My carbs are the scat pack carbs. They are mechanical linkage with accelerator pumps. The vacuum carbs were not happy with this set up.