As far as I know they don't use the same shell plate or locator buttons. Take a look at http://gunwiki.net/apps/calconversion/ - it can calculate which parts you need, but my guess is that you'll need a complete calibre conversion for .40 S&W.
On Brian's store page, it says that 40 works with the small or large casefeed assembly:
http://www.brianenos.com/store/dillon.650.html#casefeed
That's not the shell plate - you will need a different shell plate for .40
Ok, gotcha, I had the wrong terminology. Same casefeed plate, different shell plate. Thanks.