The ATS Copilot will control TCC lockup and exhaust brake engagement.

Any engine brake, really.  Pacbrake is a good choice.

Sure.  You hook up the Copilot, which monitors your TPS, MAP, vehicle speed,
overdrive state, etc.  When it detects acceptable conditions for lockup, it
will lock the torque converter (as the Copilot gets spliced inline with your
TCC lockup wire to the transmission).  Also when conditions present
themselves (TCC locked, TPS showing closed), it will energize a wire that
you connect to your engine brake.  If you have the brake armed (separate
switch you install in the cab), then the brake will activate.  When the TCC
unlocks, the Copilot de-energizes this wire, which will kill power to the
brake, disengaging it.

Specifically, the brake is controlled via a solenoid that vents pressurized
air (compressed via the on-board compressor that gets installed with the
brake, supplied from a small air tank that also comes with the brake) to a
pneumatic actuator that manipulates the butterfly valve of the exhaust
brake.  When power is removed from that solenoid, the pressure is vented,
and the butterfly opens back up via a return spring.

You'll remember we discussed some "hacks", including a microswitch, that was
needed on the '05s due to the fact that the exhaust brake programming in the
Cummins ECM was disabled by Dodge.  Because the ATS Copilot monitors the
various sensors independently, you don't need anything from the ECM, and
therefore don't need to work around the lack of exhaust brake control in the
ECM - the Copilot effectively replaces the ECM in that department.

I'd still recommend an ATS converter and valve body, to fully take advantage
of exhaust braking.  You can still use it with an all-stock transmission,
but it won't be as seamless or effective.

Read the installation instructions of the Copilot here for more info:
https://www.atsdiesel.com/PDF/120505/04-05%20Dodge%20Co-Pilot.pdf