If he installed the real Jacobs Brake from Mopar/Cummins then his converter will lockup, also he has a downshift from 4>3 around 60MpH when he pulls the Knob, Converter stays locked down to around 30MpH.
Also the warm up feature is there.
The only thing the Driver has to watch for is that the converter is truly locked up after the 4>3 downshift because the EB kicks in faster then the converter can lockup again, at this point you need to feather the Accel Pedal to give the time for a finished lockup. Otherwise it slips and this couldn't be good for the clutches.
Best way to determine if the converter is truly locked is to watch the rpms, if they drop to around 800-900 after the EB is activated then it isn't locked up.