Exhaust system question.

So I just purchased a 2002 Liberty that needs some repair. Among those repairs is the exhaust system.

I'm looking at basically replacing all of it. It's been cobbled together and welded by a middle schooler. Upon searching parts I see that the exhaust for the 2002-2003 is different from the 2004-2007. The 2004 exhaust gets rid of the 3rd cat. Which makes that system quite a bit cheaper. However the position of the downstream O2 sensors is moved further away from the cats and the O2 part numbers are different as well.

So my question to anyone that might know... Can I use the 2004 exhaust system in the 2002 if I'm replacing it all. If so, would I need to use the 2002 or 2004 O2 sensors?

Any help would be great, thanks

The OEM price for the downpipes and converters is only $100 different between the early and later versions, and I would only use the OEM system unless you plan to own the Jeep for a year or less. That's a lesson I had to learn the hard way. Anyway, the O2 sensors, connectors, and hanger at the transmission are all different. You could convert them all to work, but it'd cost you more than the difference in exhaust systems.

The Y pipe is considered a catalytic convertor pipe because it Has the unmonitored cat at the end before the muffler.
I’ve bought 2 replacement y pipes for my 03 and 02 - it was breeze. There’s a company that will make them per order for about $165 shipped.

Difference in placement somewhat between 02-04s etc due to transmissions