Oh and just on the safe side and as was discussed in the EPO-thread (which Albatros should read up on), pre-EPO Tours would inevitably lead to the usual suspects being there or thereabouts. Yes, it provided some advantages, but couldn't turn "a donkey into a racehorse".
So yes, it was possible to win a TdF unaided from PED's pre-EPO if one had superfluous physical abilities like Lemond had. Dos that mean he definitely never strayed of the straight and narrow? We will never know for sure, but until now the silence has been deafening from all quarters in the peloton. More than van be said for the likes you have mentioned (Thevenet, Merckx, Anquetil, etc.).
Regards
GJ