Cam HP capability

Engine will be a 318/390 stroker -

My target HP is 400FWHP

I have 480 HP at the head (Peak HP) (234 @.550)

Cam Card is : 282 adv, [email protected], .495 lift

The formula - PeakHP/310 x dur @ .50 says around 362 hp...

How reliable is this formula?

Assuming I have the exhaust, induction and ignition - is there any way this cam will make 400HP with the current Peak HP at the head?