One difference is that they put the gear selector switch inside the trans, vs bolted onto the top. The old style switch will still bolt on though, and you can use your stock harness with it. You would also need an 03 PCM (hardware) and a custom tune, starting with the 03 base cal. Not a bad swap, I ran an 03 trans in my 99 regal for 5 years or so, and the cars still going strong!

-Rob