The 3.8l shares the same bolt pattern as the 5.0, so you at looking for a 3.8l trans. I think after 2003 they went elevtronis speedo.
Your have to give the donor trans a performance rebuild. Stall converter, extra clutches, shift kit, cooler. Will take big power.
Another option is to have someone rebuild and AOD with the 4r70w guts.
If you are serious about building up an automatic, this is the better option. I've seen built 4r70ws stuck behind 600-700hp drag terminator Cobras and hold up to launching on slicks.
Your have to give the donor trans a performance rebuild. Stall converter, extra clutches, shift kit, cooler. Will take big power.
Another option is to have someone rebuild and AOD with the 4r70w guts.
If you are serious about building up an automatic, this is the better option. I've seen built 4r70ws stuck behind 600-700hp drag terminator Cobras and hold up to launching on slicks.