drive and the 5.25" drive on my machine somehow?

	Yes, to the 720K.  No, to the 1.2MB and 1.44MB.

	Putting a 720K 3.5" floppy drive is rather simple if you are
just replacing the existing 360K 5.25" drive completely.  In most
cases it's a one-to-one swap, providing you can get the jumper setting
set correctly on the 3.5" drive.

	You can run both drives, provided you make a mechanical switch
(SPDT) to change the drive select between the 5.25" 360K internal
drive and the 3.5" 720K (run externally).  You need to make a cable to
switch the pin 10 (FDRIVE0*) from one drive to the other.  Drilling a
hole in the case above the left fan grate is a suitable spot.

	When you use the 720K drive, all you need to do is create an
iv description file that has 80 cylinders instead of 40, and you get
the full 800K (80 tracks, 10 sec/trk).  Makes backups go faster!