I found this on ebay and ordered one for my 40. Looks to be a good setup for a 40 while retaining the stock radio opening in the dash. Is a AM/FM receiver with ipod input, sd card slot, and usb. For some reason this unit was discontinued by the manufacturer and this seller has 3 left. Just thought I'd pass it along - no affiliation.
Adjustable Shaft Style AM FM Car Stereo Radio iPod USB - eBay (item 230588071905 end time Feb-26-11 10:15:39 PST)
Adjustable Shaft Style AM FM Car Stereo Radio iPod USB - eBay (item 230588071905 end time Feb-26-11 10:15:39 PST)