I can verify that AIX/386 and AIX/370 were a common set of SCCS sources at Locus when they did the development for IBM. So if you can find the base sources for the one you should have much of the other. There were obviously some low level tools that were specific to each architecture and the compiler back ends were different.
I do not have access to any of the that, as I was not directly involved with that project, since I was leading the TNC work for Intel, HP, DEC and Sun; I was specifically fire walled from the original IBM TCF project at the time (I was one of the architects and we all got together regularly but for legal reasons, Locus was careful about who had access to what sources). I know folks that did have access to the IBM IP and I can ask around. i.e. Walker, Joe Hopfield, et al would people to ask, if you can find them.