Check out Ovett in the 77 world cup race. Also the (86?) Commonwealth games 5k. He literally looked like he was jogging at the end of the 5k. So with better pacemakers (pace lights), better tracks (Monoco over Rieti eg), super shoes (racing and training), better clothing, more competitive opportunities (Diamond League/regular World Champs - Olympic cycle) he would indeed be competitive. But so would Coe/Cram/Moorcroft/Willamson/Elliot etc etc. Don't forget how primative the shoes were back then and how much difference that would have made to training/recovery/injury prevention alone.