The spindle length matters because you will need the straightest chainline; a bottom bracket too short or too long would not make your chainline straight.
http://www.universalcycles.com/shopp...s.php?id=14284
Pick the one that says 68x107mm, basically the first one.
The crankset requires a 103mm long spinde, a 107 would work fine but you'd have to put the chain ring on the inside of the cranks. If you want to have the chain ring on the outside and don't mind paying extra $10 dollars or so...you could get this.
http://cobikes.com/shop/index.php?ma...products_id=34