LeMond started riding professionally in the early 1980s, with Renault, then teamed up with Hinault at La Vie Claire to win his first Tour in 1986. That was before EPO was used for doping - Epogen was not even sold by Amgen until 1989, and it took awhile for athletes to start using it for performance enhancement. That started sometime in the early to mid 1990s. And wide spread blood doping came even later, after a test to detect Epogen was developed, which was in 2000.
So it is pretty clear that the Tours of the 1980s and early 1990s were won "clean" - well, there were amphetamines and so on, but they aren't anything close to Epogen (and other synthetic erthypoetin) and blood transfusions in their effectiveness.
In the early and mid 1990s, riders who were at the top of the sport suddenly found themselves being dropped like used tissues. Andy Hampsten for example. LeMond was finished by then, his body was breaking down, the shotgun pellets weren't helping. His three Tours and two World Championships were indisputably done without Epogen and, as far as anyone can know, without other doping. You better believe Lance would have uncovered evidence against LeMond if there was anything to find - he was (is?) worth $100MM and that hires lots of investigators.