And its just me but I really think you need more cam although I may be failing idiot gearhead here. Blowers eat cam. My SBC cam was 255/262 at .050 and idled at 850rpm. There was definitely no lack of bottom end power. Also according to Stahl and Lemon's, 400+hp 6cyl blower motor should have 2" primaries.

"The first rule of overkill: You can never have too much overkill."
"Overkill is underrated."