I have modded a couple of PC drives to work on Amiga. I forgot exactly the basic proceedure but its pretty easy although not all drives can be modded a lot can.
The easiest part is getting it to read Amiga floppies. Slightly harder but still usually quite easy is enabling it to detect a disk when inserted. (Click Click... when no disk is in)
Older drives are easier to mod. Some its just jumpers that need setting.
There are some sites with guides.
