just because the cams are ground different for stock reasons does not mean that aftermarket type-s cams wont fit in our head. the differences between the heads on the si and the type-s have nothing to do with cams but rather flow. the type-s head has a better low end while the si head is optimized for high rpms. the dimensions of the cams in the engines are all the same, the only difference is how aggressive the cam lobes are. take a type-s cam and si cam and place them next to eacherother. you will see that both are the same length and diameter where the cam journals bolt to the head. so if they are the same dimensions, than why do you think it can't be swapped. sure you may not get the same power you may out of an aftermarket si cam vs. aftermarket type-s cam but that does not mean it can't be done.