just remeber that honda knows what they are doing, we only think that we know what we are doing. All of the different frankestien motors have inherent down falls, thay must be overcome to make the motor as good as a factory vtec motor. many people argue that they are never as good as a factory vtec motor. none the less, the head swap could be pretty cool but probably not as cool as the whole motor. frankenstiens were good with b series motors because the non vtec b series motors
(Ls/b-20) were stroked longer than b series v tec motors. this was good because it would yield a bunch of torque. all of the k 20's( if i'm not mistaken) have the same bore and stroke. therefore what would be the advantage to swaping just a k series head when you could do a whole different k series motor that was engineered from the ground up to work with that head. the only advantagecould potentialy be price. but
A. your friend is apparently wealthy
B. like someone else said the head would probably cost as much as the whole motor.
now, a k24 with an 02 type r head or an s2k head would rule.