I think Pre would have been able to get the bronze ahead of Brendan Foster in the 10,000m in Montreal in 1976, he would not have been able to beat Lopes and Viren. In the 5000m he would never have had a shot, he was a strong runner but never had the last 400m speed that is required to medal against that field (Dixon, Quax, Viren, Hildebrand).
So hypothetically, Pre could have been an Olympic bronze medalist at best (in Munich had he run smarter, and in Montreal in the right event). Then the Olympic boycott in 1980 and that would've been that for his career.