Well, this case surely ought to be large enough!  And don't worry, Commodore enthusiasts, I didn't wreck a perfectly good C=1541 drive for this project!  A couple of years ago, I picked up three of these from the local Goodwill Computer Center (note the "Goodwill" price sticker still on the case) for about five bucks apiece, and hooked each one up to my still-working C=64 to see whether or not they still worked.  The other two tested out OK, but this drive wouldn't read discs at all, nor would it format and write to one; every command sent to the drive just resulted in that thacka-thacka-thacka head-indexing sound we all remember so fondly (at least until we realized it meant all those "copy-protected" game discs were beating our $400 disc drives to death!), and then an "error" blinking of the red LED.  It's dead, Jim.

Cracking open the case, which is as simple as removing four screws from the bottom, reveals the following inside:

 

Getting the old C=1541 innards out of the case couldn't be easier – the whole affair is mounted to a single metal chassis, which in turn mounts to the plastic case bottom with six easily-accessible screws. Remove those screws, and the whole thing lifts right out.  (Although considering how much it weighs, maybe "lifts" isn't quite the right word!)

 

See?  Plenty of room for the IDE drive carrier!  Of course, mounting the new USB/Firewire-to-IDE electronics is going to require a little more work...