Help Electrical Dummy

[Chevyholic]

So, I can add new circuits and install all kinds of lighting and electrical services to my home, but haven't figured out how to transfer that knowledge to a car. Here's my problem/question:

How do you keep your lights from dimming and windshield wipers from slowing when going from running speed to idle? When I come to a stop and my wipers are on the slower speed they have a hard time even tracking across my windshield and will sometimes come to a complete stop due to the friction. Will an upgraded alternator help this problem? If a new alternator is the answer, any suggestions for a replacement? Mine is currently externally regulated, so I'd like to switch to internal, but see all kinds of options for amperage, but don't quite know how much is enough, or too much.

Thanks!