You're right Tyson still had a good chin by 2003 and Toney was not a puncher at HW but I think Mike would have been stopped more by exhaustion than Toney's punches.
Doesn't matter how good your chin is if your gas tank is trash and you're just sitting there getting nailed all night. Tyson's legendary head movement of the past was only good for like 2 rounds at this point of his career and his foot speed was gone. Unless Tyson manages to stagger Toney with a sudden explosive combination and the ref is very quick to stop it, he would just become a sitting duck after blowing his load attempting to take out the chubby defensive wizard.
Mm- Well If half a year ago he took a drumming from Lennox I have my sincere doubts about Toney stopping him early. I think he just shoots his load early and gets beaten up inside with very little resistance. Unless he catches Toney flush by something big what hope does Mike really have? Toney is the former MW who called out Wlad and Vitali no issue with balls here I think Toney makes this as rough as it needs to be and gets surgical with his hands for about 8ish rounds before the ref has seen enough. However if we even use the version we saw against Bus or Vander ect any number of versions of Mike destroy Toney just not the worst.