To give it a try without too much investment check out this thread

http://www.bikeforums.net/showthread.php?t=98174

It was dicussed today

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.

Thanks for the info. I am thinking just like the guy in that other thread - beater bike for rides with my wife....

I personally have tubes and tires laying around, but as for the wheel/hub combo with cog and lockring, I paid 76 dollars at my LBS.

As for your bike, I'd say give it a shot. You may find that the chainline is off with the reasoning because of the crank (somone said somthing about the one peice crank/large chain ring) that'd be the real problem. But if you keep your gears low, a slight missalignment in the chainline won't be disasterous. i've broken a chain or two because of misaligned chains and then mashin on gears.

Push comes to shove you buy a new bottombracket and crank, perferably used. And if you lucky enough like me there's a used bike shop in town and you can just go pick through their "junk"