I would second to reconsider going with 650b wheels/tires for touring purposes. It is so much easier to find 26" tire replacements than 650b whether you're touring the U.S. or abroad, unless you don't mind waiting a few days for a mail order to arrive. 26" will also give you more room to run wider tires and fenders -- part of the original intent for this frameset. Whichever way you go, choose a good rim, good hubs and double-butted spokes. Velocity makes some good rims. I suggest the Aeroheat if you go 26".

Tires - Should you go with 26", I personally love the Schwalbe Marathon Racer.

Omiak is right about the BB7 brakes on the Surly LHT Deluxe frame. You cannot run disc brakes. I believe Shimano has some nice canti brakes: the CX50. Paul Components' Touring Cantis are highly coveted but they are also super expensive.

+1 on Tektro cross levers.