What types of motherboards will fit it? I'm guessing ATX but I don't really know.
You're up for a real challenge if you want to put a different mobo inside a 6400 case.
The mobo was slid into the case and held by an edge connector, which will add an extra layer of fun to installing a different board (ie you may find nothing to mount the board to)
You'll find a lot of info Here
And it's a narrow case...not much wider than the CD drive. You might get away with a micro or mini format motherboard. Anything bigger and you'll be bumping against the non-ATX PSU or the drive bays.
In short, the case is a complete bugger to work on, and you'll get a gold star and many geek points for a successful recase.
Aww, well that's a bummer... the reason I was hoping to use the case is because I liked the design and it seems quite rugged, but it looks like it won't be simple...
Thanks for the answer anyway.
Pretty much the only board that would fit in there without some major surgery would be a MiniITX format. Even then you'll be up for some surgery to get access to the drives.
The 6400 logic has a front edge connector that slots into a ribbon header at the front of the motherboard cavity. This makes the connections between the board and everything else in the machine. If you can get the pinout, you might be able to make up an edge connector* that adapts to plugs for the ITX board. Whether there is enough room for this as well as the motherboard is another question. I'd suggest you look up (and/or measure) the dimensions of both before continuing.
Take the rear plastic port cover off and slide out the motherboard. You'll see what I mean
*(further hints available if you pursue this)
I have a 6500/225 I plan on pulling the LB and putting it into a Color Classic with a G3 upgrade (a future project).
The darn case weighs 44.5 lbs!
I think if I liked the look of the case (it actually is kinda cool) I would investigate removing the outer plastics and installing them around an appropriately sized PC case then you would be less limited in motherboard while still maintaining that late '90s Apple cache´ :^)
If it is possible, it would probably save you a few bucks too.