450, you don't know what you have until you really push yourself ;)

La Crosse can't be that hilly, and no, I am not going

edit: don't forget to get off you bike and run some at top for your tri training

edit 2.0: 380 would likely be good if you wanted steady state the whole way and really it will be close since the flatter portion at top is not that long after the climb. you could try 390 until it flattens out, push a tad more at that point while getting as aero as possible and then limp across the line(aerolly invisible)