Which one will fit in the A3000 desktop model; the one with narrow window in the front panel (or two in my case). See attached picture url http://upload.wikimedia.org/wikipedia/commons/6/65/Amiga_3000_Front_Enhanced.jpg
I prefer not to make modifications to the case if that's possible.
Thanks.
Short answer: You can't.
Long answer: You probably could if you found some type of stand off to place in the bottom of the SCSI Card reader to lift it up high enough to get either the CF card slot or the PCMCIA card slot to fit through the opening.
You can put it in an external SCSI case.
I put mine in the hard drive slot. When I was setting everything up I did this:

If you want access to all the card slots your only option is to either modify your case (don't do this) or make it external.