I have a 2000 Chevy tracker with a 4 cylinder, automatic and was wondering if a 2004 Chevy tracker 6 cylinder, automatic will fit and if the wire harness will match as I have the opportunity to get it if worth while, thanks

What is it you're asking about - swapping just the transmission - or - the entire powertrain (engine & transmission)?

As far as I know the transmission will interchange, the engines can also be swapped but that's a fairly involved task.

I can get both motor and transmission to replace just wanted to know if it will fit in and if the wire harness is the same.

Hoping someone can give me some more advice

What more advice do you need - as far as I know the transmissions are interchangeable, and whilst the engines can be swapped, it's not going to be a simple swap - you didn't really expect the four & six cylinder engines to use the same wiring, did you?

Swapping the engines will require pretty much everything to be swapped, engine, cooling system, wiring, ecu, intake & exhaust - and if you want to do it properly, the front & rear axles (the gears are different)

Thanks