The only way I can think of is to use the 7.5 Network Install Disk (floppy) and make sure it has all the resources to file-share via AppleTalk over Ethernet. Just boot off the floppy, connect via AppleTalk to your Indigo iMac (make sure that one is temporarily set up for AppleTalk via Ethernet as well), from there you can open up the 7.5.3 installer that's stored on the Indigo's HDD and clean install to the PowerBook. You'll need an AAUI to Ethernet adapter for Cat 5 network connections. If you don't, then you'll need the AsanteTalk Ethernet to LocalTalk Bridge. Asante still sells them for $78 USD luckily.
73s de Phreakout. :rambo: