TheMacGuy's mounts were the wrong ones. I'm still on the lookout for the proper ones for a 12" PowerBook G4, of course (I may also have mine somewhere, but there's a ton of junk I need to sort through first).
Anyway, I have mostly got the Indigo iBook operational.
The DC-In jack needed repairs (it had broken solder joints, with some burning on one of the pins), the Modem jack needed to be resoldered to its board, replaced the trackpad cable, and I gave it a good cleaning.
It works OK, but I think the HDD cable is bad because formatting a known good hard drive results in Disk Utility producing an Input/Output error, and the trackpad button won't un-click without help, so it still needs work (specifically, it needs a new top case and HDD cable). Oh, and the badly faded colored areas on the casing are a problem too, albeit a purely cosmetic one.
I have a lead on one with better plastics in southern California, so I'll see if I can get that.
So, it looks like I've gotten all three in working condition. What an accomplishment!

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