What do you mean by OEM? There were quite some branded SGI workstations sold, e.g. from control data, but as far as I know, they all ran standard IRIX.
The set of installation CDs for IRIX 6.5 is splitted into two parts, one is version specific (overlays, (complementary) applications) and one is not (foundations, dev. libs). In theory, developer foundations are also not version specific, but as it turns out, there exist two revisions of dev. foundations and later IRIXes want the later one (part-nr. ending with -03 instead of -02).
btw, you can get IRIX 6.5.22 overlays from SGI for free after registering in supportfolio
The set of installation CDs for IRIX 6.5 is splitted into two parts, one is version specific (overlays, (complementary) applications) and one is not (foundations, dev. libs). In theory, developer foundations are also not version specific, but as it turns out, there exist two revisions of dev. foundations and later IRIXes want the later one (part-nr. ending with -03 instead of -02).
btw, you can get IRIX 6.5.22 overlays from SGI for free after registering in supportfolio