I believe the 53005 is recommended because it slips on and can be welded without additional adapters, etc. It's also dirt cheap (allexhaust.com is reliable and has free shipping and the best price when I was shopping).
My suggestion would be to replace both of the rear ones, which will prevent any imbalance in backpressure (and you don't have to worry about the other one dying). Both are high-flow, but that way you're sure they are the same. Also, you will probably get a bit of a cut on the labor since they are already right there.
Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy; its inherent virtue is the equal sharing of misery. (Winston Churchill)