You'll probably need a BB axle that is ~5mm longer.
Since it's a triple being used as a double, you'll probably also need (5) 3mm chainring spacers to space the granny ring inboard from the crank, and the chainring bolts will have to be a little longer to get to the threads in the crank. I have a triple like this that I am currenty running as a double.
You may also have to look at getting a new rear derailer with a long cage since triples require more wrap-up capability. However, if you run a pretty tight cassette (e.g. a 12-23) and are careful about not using bad combinations, you can get by with a short cage rear derailer.