Generally, the casing should be grounded on electronics like that. The body of your car is ground also. If you saw an arc between the casing and the body of the car while it was running, that tells me that the ignition box has a poor ground. I'm assuming you took care of this when you re-wired right? Make sure its cleaned piece of metal (no rust or paint) and of proper gauge wire. Maybe its an internal problem with the unit and it has a weak ground connection on the actual ground wire (corroded, partially blown trace, ect.) and was getting a good ground through the casing (would explain the arcing), if thats the case, ground the casing to the chassis of the car too... poor ground on the box may explain the car running rough.. maybe not, but at least you can rule it out after that.
As far as the regulator, I'm not too sure, I haven't had my car together in a long time, much less know even where my alternator is, come to think of it... I think they are internal on these cars, meaning inside the alternator, but am not 100% on that one... hell I'm not even 50% on that.