With the fairly conservative HP/L figure you are seeking, that goal is not going to be hard to obtain with the siamese head and other performance components available for these engines. I have built several 250's that have made 2.05 HP/CID, and were very reliable race engines, and still used the "lump" siamese head. Sure a multi-valve head or even a "Cammer" style head would be very exotic, but don't sell short the potential of the existing technology on these heads. I think if you don't end up with a better head or combination than what you could have with the siamese style head, you really haven't gained anything, for all the work involved that you had to do. Its still an interesting project to consider, and would like to see how you proceed with it....
I have to ask how did you pull 512.5 hp out of a 250? Thats 125hp/L... The Honda S2000 squeezes 239 hp out of a 2.2L and thats only about 109hp/L and the Cosworth Duratec gets 260 hp out of a 2.3L which is aobut 113hp/L. I am in now why trying to discredit you, its just these are two new performance engines with all the modern bells and whistles of today(that rev to 8000+), and they still do not hit that kind of hp/l number(125hp/L).
