In my opinion, for the purpose of bench-testing, I think your best bet is to:
a) ask Whelen for a copy of "SC Programmer" (assuming you have windows PC?). (They sent a copy to free-of-charge last year after a simple email asking for it, FWIW)
b) Obtain a RS232-RS485 converter (search this site for lots of advice on things that worked for people).
Assuming you have the above in good working order, run Whelen's SC programmer and use the "Simulator" function to talk to your light bar and explore its exact configuration.
Otherwise, you're somewhat dependent on luck for someone to have an MPC01/02/03 that perfectly matches your lightbar. Some stuff might not work. It doesn't mean its problematic, it just means the MPCxx isn't configured to exactly match your device. SC programmer lets you experiment and explore your device.
On the other hand, given the description of your lightbars you've provided, if there's anyone who recognizes they happen to have an MPCxx configured exactly for your device, they'd likely be here
.