The HIII kit I had (and sold) came with the midrange driver & horn, the tweeter driver & horn, the new 12" driver, and the crossover - truly plug-n-play.
Places like Orange County Speakers (local to you) or Simply Speakers (not local) can't recone them? That would be the easiest choice. I would second the advice on the Crites drivers, I've had nothing but good luck with Bob's stuff.
K-701 horn & K-53-Ti mid (same as the HII & Cornwall III). I had to talk them into selling me a pair because they couldn't get past the idea that I would use them in Quartets and not the models they were "designed" for originally.
I've got a pair with Crites tweeters, klipsch titanium mids, and upgraded crossovers. They sound great and are very similar to my Forte II's. I think that they are easily the best bang-for-the-buck in the Heritage series.
Jim