I actually built a MAME machine from Bad Dudes machine. The first thing to know is...
Unfortunately, Bad Dudes control panels are CRAP! They're metal and the layout doesn't provide good use. It was barely good enough for bad Dudes. If you'll notice, the buttons (and joysticks) are set at an angle. This makes it useless for 4-way games because up is more like "up and to the right". Also, the buttons on either side are nice for lefties, but useless for anyone else. In the original game they were just mirrored. But in any other game, you can't be reaching across the joystick from both sides to reach all your buttons. That being said...
You'll find yourself having to replace the control panel or drill it out from scratch. However, if the latter is the case, you're probably just as good off with making a new one.
I built a pretty big "franekpanel" over mine, but it fit well (at least better than most). If you don't want more than SF controls, you can fit them cramped on the control panel. However, if you want virtually anything else you'll need to build some sort of attachment.
I'll try to get a picture posted of the Bad Dudes machine of mine.