The single best thing (for me) about mid years is the fact that 74-75's don't need to be smogged in CA! It seems to me that the short hood/impact bumper cars are getting more and more desirable, most likely driven by the prices of the long hoods....and out of these I would bet the 74-75's will be the most valuable. Check out my 74 911S Hot Rod build here:
http://forums.pelicanparts.com/porsche-911-technical-forum/662026-1974-911s-930-hot-rod.html