What is the highest amp rating alternator I can use on a 1970 Dart

An alternator shouldnt cause anything to catch fire or smoke. In audio world we run 3 300 amp alts at nce. You just need to make sure it has a regulator. A bigger alt just has to do less work. Maube its different for old cars, but a friends 82 suburban ran 2 250a without a problem.

*Some are externally regulated which if you dont regulate will cause a battery to charge over 12-14v which can hurt electronics*