It's not unreasonable that doping has some relevant effect in performance. But much does talent and skill. Look at Coppi's 1950's ascent of Alpe d' Huez at 41:00 - so you say he doped? Even if he did - the only thing they had in 1952 was amphetamines. Meth is not going to get you a 41 on the Alp d' Huez.
I google searched for you. His time was 45:22. Pantani`s record time is 37:35 (don`t think it is known if it was precisely the same distance).
http://en.wikipedia.org/wiki/Alpe_d%27Huez
I *think* that equates to around a 20-25% increase in power (W/kg). I`d put little of that down to technological differences, training etc and most of it down to Pantani`s haemocrit level (64% in 95!) People like Coppi, Merckx would be competitive today, as they knew how to train (and had talent and skill, like you mentioned), so I doubt modern training methods would have made much difference to them.
http://www.sportsscientists.com/2007/06/drugs-work-but-by-how-much-look-at.html
Drugs:- He created his own mix, renowned as "la bomba," that included amphetamine pills, cola and caffeine.
http://history.top10-digest.com/the-history-of-doping-in-cycling-10-prominent-cyclists-who-were-accused-2/
Precisely the performance gain from doping is hard to know, but I think Hamilton cites how he went from 2nd at the T De F one year on a full program and with a broken/cracked collarbone, to 94th the next year when cut out of the loop. But don`t forget, PED`s aren`t just for pure performance gains, they also prevent performace deterioration from the effects of fatigue during grand tours. Performances that don`t decline over three weeks and get better in final TT`s...
as anyone who is even slightly 'mod' related would understand the tight connection of certain pharms with the culture - would also KNOW that he is straight up, by the same token.
Interesting argument. Anyway, time will tell.