It's fugly, but no doubt you'll find it much easier hacking up a an AT or Micro ATX case. A decent quality one from a HP/Compaq/IBM would look reasonable. I don't know where you'd fit the power supply in a IIci/Q700 case without it sticking from the top, and have enough room to keep the existing 3.5" floppy and HD brackets inside.

Have a spare Q8x0 steel lid? You could always ahem put a hinge on the side panel for easier access