If it is a Japanese made LeTour, then it is a sin to convert it. Some of the nice bikes I have seen ruined by this latest fixe and single speed fad really breaks my heart.
But it looks like the LeTour you have is something from the 1980's and probably not one of the Japanese made LeTour as you pointed out, so have a ball. At least keep all the parts you remove and have them handy for the next guy or for after you get tired of the single-speed/fixe.