Im not an expert but theres NO WAY your gonna have 550hp with a head that flows only 239cfm. My J-heads with 2.02/1.60 valves flow 284@525/530 and im hoping to have around 500hp-525hp.
I don't know what HP it will make the engine guy said he is hoping for 550HP weather it does or doesn't who knows I don't really care either way as long as it runs hard.
I will have to dig out the paper work for the heads I might be wrong but I remember when I picked the heads up the guy told me that they were capable of over 500HP I just had to get the rest of the motor there.
I guess it is a wait & see game that we'll all know about in a few months when it is done & run.