there plenty 250whp b series and we talking about 3k alone in bottom end
the head would have full race port and polish
you would have to run atleast E85 to that type of power
compression would have to be at least 14.1compression man
i hate k series because of transmission problems but overall k is easiest motor to hit 250 on pump gas
h22 jones has realiable 250whp on pump gas driven everyday and beat on ocassion
h2b is one greatest overall set up
but good luck man on the build sounds like you have great goal