I've never heard of it and none of my reloading books even mentions it.  It may exsist but it could be a wildcat round that either he or someone else came up with.  Are you sure that he isn't taking about the .444 Marlin?  The .444 Marlin is a straight walled rifle round that Marlin came out with back in the late 60's or early 70's from what I can remember and I have seen Encore pistols chambered for it. 

If it is a actual round I would like to hear the specs for it. 

Sorry, I just checked and it is called "445 super mag". Sorry for any confusion.

The round would be a fun one to play around with but it is basically a wildcat with only one or two companies offering ammo for it.  So if you don't reload or know someone that would reload them for you there is really no reason to chamber a round for it.  What it does is takes a .444 Marlin case and shortens it to the desired length.  You would have to neck ream the case to a uniform thickness and then load it. 

A better and easier route would be to purchase a .454 Casull barrel for the TC and go with that.  At least you can find factory brass and ammo.  To change your .44 mag barrel to the .445 Super Mag you are going to have to find a gunsmith that will ream out the chamber and possibly have to purchase the reamer die for him to do it. 

In my younger days I played around with a lot of wildcats where you needed to make your case out of another round and I have found that unless you like doing that kind of stuff that there is a factory round that will work just as well with none of the problems. 

The 445 Supermag was/ is a Dan Wesson Firarms cal.  Dan took the basic Mag pistol cals (357, 41 &44) increased the case length, crammed in a bunch more powder and called them supermags.  You will not be able to find factory ammo but should be able to find brass ans dies to reload.  Dan Wesson and his supermags had /have a dedicated following.  They were good guns and calibers!

Critter nailed it when he summed it up:

In my younger days I played around with a lot of wildcats where you needed to make your case out of another round and I have found that unless you like doing that kind of stuff that there is a factory round that will work just as well with none of the problems. 

Biker