Hah?
As I understand it, cylinder head castings go something like this...
#2685 (late 258 - will fit to 4.0L)
#2686 (RENIX - 1987-1990.)
#7120 (1991-1995, OBD-I. Exhaust ports raised 5/8" from location on RENIX.)
#0630 (1996-1999 (TJ/WJ)/2000 (XJ). OBD-II head without COP/DIS ignition)
#0331 (2000-2007 (WJ/WK/TJ/...)/2001 (XJ). OBD-II head with COP/DIS ignition.)
The #0331 casting seems to have been revised at some early point - as I've not seen too many reports of cracked heads beyond about 2002. However, I've yet to be informed just how to determine a "revised" head from an "early" head in the #0331 setup, and I'm still working on that.
The #0630 head may be readily adapted to the #0331 with fabrication of brackets to hold up the coil rail, but it's worth noting that the exhaust ports were reduced from the #7120 to the #0630, and a bit more with the #0331, to improve catalyst light-off time. OBD-II may throw a minor fit if you swap on a #7120 head - but the #0630 head has been swapped onto OBD-II rigs without any trouble (since it's an OBD-II head anyhow.)
Yes, all five of the casting numbers will bolt onto the 242ci block (and the late 258ci "wide deck" block - 1975 or so forward.) However, the port locations did change significantly, and the flow characteristics of the heads also changed - and OBD-II is picky about things.
Whoever told you that a 2686 head will fit your application (which is OBD-II) is only half right - while it will fit mechanically, you're in for a headache making everything line up.
As far as "brands" - there are really only two. OEM and the aftermarket aluminum head (no idea who actually makes the thing, but it's available through Patriot Performance and HESCO.) What you're looking at is typically an OEM head that has been cleaned up, machined, and reconditioned to "new or better" specs - but all will be the same basic casting. The only change is who is actually doing the work.
Just about any iron head you're going to find for the AMC six will be a reworked OEM head - cast by/for AMC or Chrysler, and (by definition) used. Nothing wrong with that - for a full-out performance engine, I have long preferred used engine cores to new, and most big-name engine builders do as well. The only "new" heads you're going to find will be either going to the dealer (if they have them on the shelf - and probably a bare machined casting) or getting the recent aluminum head from one of the sources given (which you can order fully assembled and ready to bolt on.)
