I should have done this before posting, but I just measured the motherboard currently installed and will need either a Flex ATX or Mini ITX motherboard to fit correctly. Unfortunately, I was hoping to have this be a low-budget system, and both those options seem too expensive right now for me. However, I also have a (very) old VCR that doesnt' work anymore. It is about the same height, but much longer and wider. That'll make it much easier for me to fit everything in, even when using an ATX motherboard. Still, because of the height, I am worried about everything fitting in.
The old computer I had originally planned to gut was a Centris 610 (like the pic except w/o optical drive)
. Fortunately it still works, so if I ever find a mouse and keyboard to work with it, I can use it.