Wire gage size?

I am going to rewire the Dart and was wondering if I up all the gages one size would it be sufficient...I am going to run a higher amp alternator and am planning at the minimum of 10 gage for that...but was just wondering as I am going to upgrade headlights to a style slantsixdan talked about...but other than that everythinh else will be pretty much stock...also where can I get better bulkhead connectors and just new connectors in general?