Cam Selection

I originally built my 400 with flat top pistons with no valve reliefs at zero deck. I think you are going to need to stay under 500 lift with that combo. I ran an old Crane grind which was 467/494 lift, 222/234 duration, and 114 lobe centers with no trouble. It made 415 HP and 450 TQ on the engine dyno with basically the same parts you are using. Summit still sells essentially the same cam under their brand name SUM-6401. It had a decent idle and a very flat torque curve.