I have very limited knowledge on transmissions, hopefully someone correct me if I'm wrong. I do believe one year model, between late 2000 and early 2001, had what was called a Mechanical Diode that was prone to failure. It is still a 4R100 Transmission.
The early '99s had a different converter, lockup solenoid, and pump body. All late '99 and later are interchangeable.
Having said that, you don't want one from the first half of the '01 model year, unless it's been rebuilt. That's when they had the mechanical diode one way clutch. It was a disaster. The trans is interchangable, it is just that the mechanical diode has an extremely high failure rate.