AT&T 3B2/400 searching of components

Hello. Today I began to work with one AT&T 3B2/400 received from Austria this week, together with five terminals (4 Amtec and 1 Olivetti). The system has 4Mb of memory plus one 5.25 floppy, two mfm hard disks de 72 Mb, and one Olivetti ST/60 tape unit. Together with the system I've received a set of manuals and software. About boards, it comes with three boards that supply 12 additional serial lines plus three parallel lines to the system. All appears to work. The unique problem is about the development system (C Language), not installed actually; and the limited amount of serial cables (only two). I must check the floppies received. System is AT&T Unix System V release 3. I should like to know if someone has (or know of someone) some additional board(s) or complements of interest for this system (more serial cables, memory, SCSI, Network boards, etc). Same for manuals, even when I've received a good bunch of them, I have the impression that development system manuals aren't here. Thanks Sergio