A lot depends on the Letour... if it's an older seventies model with the ashtabula style crank (ie 1 piece crank) it might be a harder conversion. Eighties ones are probably fine to convert; they might be Panasonic (japanese) or Mississippi built and tend to be lighter, with cotterless cranks. On the other hand, those older Schwinns are some of the most indestructible bicycles ever made, if heavy. What you lose (gain?) in weight you gain in insane durability. Also, few people want to steal them, because they lack much cachet. A good choice for urban beater.