Let's say a z24 driver doesn't like to go buzzing down the freeway at 2600rpm at 70mph, and wants to swap out the 3.9 FDR for something taller, like 3.05:1.

I notice the 3.4 Alero has a 4T45E at 3.05:1, would the tranny from a 2001 Alero 3.4 drop into a 1997 z24 with a bellhousing swap? Or would it be feasible to drop the Alero's final drive and chain drive into the 4T40E?

Any other ideas to drop the rpms without changing tire size?

I assume a 4T60E from a 2.4 Achieva won't fit in the Cavi.

the amount of time and effort to do all that you might as well just buy some bolt ons
buy a header catback and cold air and your car should burn less gas if you keep your foot out of it.