The model 450T is the 45Colt the titanium snubbie (I have one in the neat flat blue finish). The 445T is the .44SPL. I doubt you could have change the barrel as it had a stainless liner and titanium barrel shroud. I know of no gun smiths who will even work on them. Have you called custiomer service at taurus?
Taurus no longer makes an all titanium revolver and you will find it is one of the few Taurus that will go for a lot more money than it cost.