On the evening of April 24th, 1984, I was walking around in Barcelona after the conclusion of the seventh stage of the Vuelta (back then it was ran in the spring), when I casually crossed paths with a young journalist of L'Equipe. 
Being new to the environment of professional cycling, I did not know him and that was the first time we met. 
After a brief exchange of a few words, he told me literally referring to a great French cyclist: "He won his Tour de France's in a very artificial manner: beaucoup, beaucoup de corticoides." 
I was surprised that a journalist who "lived by" cycling could come out and confide such a statement to a stranger, considering I was also the team doctor working for for Francesco Moser, then rival to the French cyclist. 
I asked him: "And the controls?" 
"No controls" he said, shaking his long hair. 
Naively surprised and a little disappointed, I didn't pose the next logical question: 
"No controls for him, or no controls on corticosteroids?". 

I do not remember any cyclist having tested positive for CORTICOSTEROIDS, although they were widely abused in the peloton at that time, despite having the "Thevenet scandal" of 1978 shed light on the problem. 
In fact, these drugs were not sought in the tests until at least 1999 (guess on who: Lance Armstrong, of course, in whose urine were investigated and measured infinitesimal trace amounts of triamcinolone (a corticosteroid), consistent with a legal local administration in the form of ointment). 

TESTOSTERONE and ANABOLIC STEROIDS have been available from the 50's and 60's, and it is very likely that athletes have made wide use of those, but tests for the probable intake of exogenous testosterone were approved only in 1986, while specific tests for the numerous anabolic drugs were developed as new molecules were coming on the market. 
I asked a Grand Champion of the 70's which drugs were used in his time. 
"Amphetamines, cortisone" he said. "Decadurabolin, durabolin, sustanon?" I added. "Ah yes, those too..." (he had not even considered them as doping...). 
In reality, many athletes, not just cyclists, continued to take testosterone and anabolic steroids (orally) away from the races, until out-of-competition controls were finally established a few years ago, which are an effective deterrent. 

The first scientific publication on the effects of blood TRANSFUSIONS over aerobic performance dates back some 67 years ago! (Science 1945, 102:589-591). It's very likely that endurance athletes have used it since the 60's, though only a decade later we had contextual certainty. 
As of today, there is no test that can demonstrate autologous blood transfusion. 

At the end of the 80's, ERYTHROPOIETIN came out and only in 2000 a specific test was approved, however, subject to some adjustments in time and criticism from the scientific community. 

In the same years the use of HGH and INSULIN began to spread over, for their anabolic results and effects on body composition. Only very recently specific blood tests have been developed. 

Therefore, at least since the end of the last World War, athletes have had access to drugs and methods that can affect athletic performance and theoretically EVERYONE could have been using them for many years, without running into the network of anti-doping controls. 

Professional sport (not just cycling) has evolved to the levels that we know today thanks also to drugs or at least in the presence of drugs or methods used with the goal of optimizing performance. 

But how truly effective are these "aids"? 
How much of the placebo effect is in their use? 
To what extent are the sensations reported by athletes reliable? 

Difficult to answer. Scientific studies on the topic are often inadequate and come with conflicting conclusions. The athletes and the media tend to overestimate the effects, with the result that they are considered indispensable to compete with opponents who may use the same methods/substances. 

LANCE ARMSTRONG, during the recent interview, said that he didn't think he could have won all 7 Tour de France's without using testosterone, EPO and blood transfusions. 

I think Lance is wrong. 

If his way of taking TESTOSTERONE was the one reported by several teammates (microdoses diluted in olive oil, under the tongue), this could not have more than a PLACEBO EFFECT. 
The amount absorbed with this mode of administration and dosage are negligible and certainly have no effect on performance or recovery. 
In the case of Armstrong after the disease, it is possible that exogenous administration of testosterone may even worsen his aerobic performances (Med Hypotheses 2007; 68:735-749). 

EPO and AUTO-TRANSFUSIONS, always in the manner reported by teammates (micro-doses of EPO and 1-2 units of blood) correspond to an increase of Hb-mass by 5-10% for an endurance athlete weighing 75 kg, who has 9-10 liters of blood. 
Such increments of Hb-mass correspond to performance improvements in the order of 3-6%. 
Equal increases in Hb-mass can be achieved with appropriate periods of altitude training (J Appl Physiol 1998, 85:1448-1456, Int J Sports Med 2005; 26:350-355, J Appl Physiol 2006; 100:1938 - 1945, Scand J Med Sci Sports 2012; 22:95-103). 

Therefore Armstrong would have achieved the same level of performance without resorting to doping, also thanks to his talent which was far superior to the rivals of his era.