I assume this is pitting both heavyweight at their best, probably the Ibeabuchi of the Tua or Byrd fight against the Peter of the Klitschko fight. Both strong fighters with good chins and power with not so great defenses. I will go with Ibeabuchi, due to his greater speed, by decison or a possible late stoppage.
I think Ike's workrate gives him the edge on the scorecards in a very entertaining war. Probably wouldn't be any knockdowns. Peter's sloppyness and excess weight cost him, but he does likely manage to hurt Ike with his thudding power and relentless aggression which could win him maybe 4-5 rounds.
The fact that Peter could take Wladimir's punch without a flinch shows that he is more than capable pf taking Ibeabuchi's punches. Probaly Ibeabuchi unanimous decision.