Difference between 96/97 and 98/99 exhaust systems?

I'm replacing the original exhaust on my friend's 1997 RAV4 2WD 4AT 5-door, 49 state emissions model. The central pipe housing the second cat is broken. I intend to replace this central pipe/second cat unit, as well as the header/front pipe, with Bosal OEM replacement parts. While I'm at it, I'll do the resonator/central pipe and muffler/tail pipe.

My question to you all is: what's the difference between the 96/97 and 98/99 exhaust? The later models have 7 extra hp and it seems that they have only ONE cat, mounted under the center of the car, while the earlier models have an additional, "initial" cat wedged between the front pipe/header and the manifold.

Different parts websites-and even different Toyota dealers-tell me something different. Who here can tell me straight up what I need to know? Also, how hard will it be to detach the original header/front pipe from the front cat (everything to the rear of this point is being thrown out)? Will penetrating grease and a ratchet/socket suffice?