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I used this tutorial when buying my used bluetooth module on eBay:

http://www.xlr8yourmac.com/systems/Mac_Pro/Bluetooth_MacPro_install/Bluetooth_MacPro_install.html

Granted you could probably get a model that has a newer version of Bluetooth but all I wanted it for was to use my Apple Wireless keyboard and trackpad with my Mac Pro 1,1. It cost me all of $10 delivered from a USA seller on ebay. To mount it, all you need is a couple really small screwes that I happened to have lying around (although initially I couldn't find appropriate screws so I connected it and it stayed just fine for several weeks only thing holding it in place was the connector to the motherboard).

As for Airport cards, You should be able to order a used one off of ebay as well. I looked for new ones to upgrade my 2006 Mac Mini, but they were still running $50+ for new. I just did a search for "airport mac pro" on ebay and found several (mac pros had the wireless N vs the wireless B in my 2006 Mac Mini). I haven't added a wireless card to my Mac Pro simply because it will always be hardwired, so no point in spending the $10-15 on ebay. I ended up with one of the Aiport wireless cards with the broadcom chip and it seems to work fine in my Mac Mini (no reason it shouldn't work in the Mac Pro).
 
Search here and with Google for postings about which antenna lead to connect to the BT module. In some cases (I think it's 1,1 Mac Pros only) the leads are mismarked.

I installed BT in my 1,1 and did have to connect it to the "wrong" lead to get it to work right.
 
I just did this modification on mine. apparently as they indicated above, you are not supposed to connect the BT lead, but a numbered lead to the card instead. Like the above poster I had to hunt around for screws for it. A good place to find screws would be old floppy drives or VHS players with metal racks. Or you can just buy the screws.

the range is pretty good, and the card worked right away.
 
Before you buy any module, make sure the antennas are actually present in the machine! On my refurb MP 1,1 I could not find them when I wanted to upgrade.

Perhaps they somehow had slipped behind the motherboard, but I didn't bother to completely disassemble the machine, as the reception of the internal modules was said to be mediocre anyway - so I went for USB dongles...
 
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