Possible but expensive. Here are the part numbers for a 2009. Google the part numbers.
Processor Heatsink, 8 Core, A 076-1329
Processor Heatsink, 8 Core, B 076-1330
Processor, 8 Core (need two, of course)
2.26 GHz 661-4997
2.66 GHz 661-5046
2.93 GHz 661-5047
Processor Board, 8 Core 661-4998
Processor Tray Support Plate 076-1344