Prime Shavers versus a prime Tyson? Myself I think Tyson was the total package when he fought Trevor Berbick, and from that point on was slowly but surely becoming a head hunter in the ring. Shavers prime? Somewhere between the Ali fight and the last Holmes fight.
Tyson was almost the perfect mixture of accuracy, power, elusiveness and speed. Shavers was simply the hardest hitting man to ever set foot into the ring. Shavers had stamina issues, it was a known liability that if he could be pushed passed five or six rounds you had one helluva chance.
Tyson, despite his critics, had a cast iron jaw. He took a beating for 10 rounds against Buster Douglas, took a massive beating against Lennox Lewis when he was passed his best. Tyson never exactly fought guys on the level (Tubbs, Bonecrusher Smith, etc weren't exactly world beaters), while Shavers all but ran roughshod over the division's best for 10 years.
Somewhat a hard fight to call, but I see a few knockdowns from both men, with Tyson winning either by late TKO or decision.