Maybe it varied some from year to year, model to model, but FWIW, my '82 Super le tour with 1020 tubing (very similar frame to the '78 le tour III and '80 Traveler you mention, I would think) had a 25.8 SR Laprade seatpost, with no shim, and it seemed to fit perfectly.
And yep, the '83 le tour luxe uses a 26.4 post, although I think we've determined it came with a shimmed post of a smaller size originally, as you say. I couldn't find the original seatpost or shim from my '83 when I rebuilt it, though, so I took the 26.4 SR Laprade from an '84 le tour I also have. I really like those old Laprade posts anyway. Both the '83 and '84 le tours are 4130 frames.
Last edited by well biked; 08-30-06 at 02:41 PM.