http://www.powertraincontrolsolution...ed-Valve-Body/
At least as far as what these dudes say you would need a modded valve body with an additional solenoid to have true engine braking. That is one of the little hang ups I have about 4l80e. PTCS is supposed to have the Mercedes Benz of controllers though and can control anything you could want to adjust from the controller stand point compared to some cheaper although more straight forward and simpler modules out there.
You can also turn your trans into a 5 or 6 speed. 6 speed would be best with different gears though. I see no real reason to not go 5 if you are already getting the VB but 6 sure seems sweet to me if the money was there.