I don't know about the buldog you have, but I have installed a nobrand system in my 84 500SEL. I spliced into the wires at the ignition switch by removing the instrument panel. I then ran these wires (10 gage) down to the passenger side and installed the electrinics there. Also, I found a great site
www.the12volt.com that has a lot of information about electrical applications on cars. I didn't see any that refered directly to MB, but the theory is much the same on all cars.