As the title states, I would like to do this.

However, has anyone else done this, before I get myself into something that's going to be hard?

Is it easier to buy the TSP catted Y-pipe and avoid the hassles?

I don't know which cats to get, which will fit (clearance) and if any of the pipes from the Y will have to be expanded or not. If welding is required, I'm just gonna go with the catted Y-Pipe.