Well, I'm not gone, if forgotten! I've been incredibly busy. I just switched from full time to part time from my long-commute job, and will do some consulting that I'll do from home, so I am just starting to work on the Hornet again. Finally stopped raining too (no garage, car is outside under plastic). I've also been working on another project, restoring a 25-year-old minicomputer, http://wps.com/NOVA4.
I've been having no luck finding a 10" clutch. I've got a 1982 258 six, a T150 trans. The driven shaft is 1-1/16" diam, 10 splines. There are plenty of 9" - 9.5" clutches for this combo, but no 10" clutches listed. The motor has a hot cam, claimed 275hp, probably closer to 250 to 225. The bigger clutch seems like a good idea, though probably not required. Street car, not racing.
There's rumors of Ford application parts, but unless someone can vouch for it having *done it* personally, I'm sticking with AMC-listed parts.
I don't have an old 10" to match up. I don't have access to enough books to do better cross-listing, and though stores have been helpful, nothing comes up without knowing what to look for.
I'm also seeing $200 - $220 for pressure plate, disk, throwout bearing.
I do have a nearly-new, used 9" clutch that I may use. It's new enough that the inked "MADE IN USA" or whatever on the friction face is perfectly readable -- essentially no wear. Polish marks clearly visible on the pressure plate.
With this used-bird in hand, and $200 for a plain old 9" clutch, I'm leaning toward using what I've got.