I have a '00 form Ohio, and it had the pre-cats. I've never seen a '00 with just a single cat, but people say it exists. I've always wondered if it was a mid-year change: at some point they just started putting the pre-cats on all of them. In any event:
'Couple of problems converting.
To change to a single cat/multi- O2 sensor layout, you would need to get a single header or make a pair of head pipes to bolt the factory cast manifold to the exhaust pipe in place of the cats. You'd need to have bungs welded to both pipes so you had a place to install the front and rear upstream sensors.
Then you'd have to weld 2 sensor bungs for the down-stream sensors into the exhaust pipe behind the under-car cat, and extend the sensor harness to reach the new location.
That would give you a complete exhaust with all the sensors.
The '00/'01 head has a revised port layout. I don't think the earlier exhaust manifold will seal on the new head, and neither will aftermarket headers. You would either have to find a factory single piece '00 exhaust manifold and add the sensor bungs, or use the cast 2-piece manifold with the extension pipes. Either way, any competent emissions tec. would fail you on a visual inspection.