Newbie Build Questions

[bikeski]

Staring to built a bike for my wife, its a 50s vintage Hiawatha in pretty good shape with straight fenders, rack and a good tank. Crank arm appears to be shot as there was a jury rigged pedal that stripped out all the treads on the crank (and worked a pretty good divot into the chainstay). So have been thinking about a BB adapter and putting in a 3 piece crank. What might the pros and cons be to this. Have seen some like this in the Gallery they look cool, although I am not adverse to using a one piece. Will probably need new wheels also. I do have a pair of New Departure hubs thinking of lacing them to some lighter weight MTB rims. Any suggestion greatly appreciated.