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

EVEN THE FACTORY knew that the bulkhead connector was a P.O.S. for larger alternators. Cars with 60?65? amp factory systems "got" what has been call "fleet," "taxi," or "police" wiring. This is a FACTORY mod similar to the MAD electical mod, IE the factory bypassed most of the current going through the bulkhead by using separate wires going through the firewall.

Fleet/ taxi:

http://www.forabodiesonly.com/mopar/showthread.php?p=1969960437

Read the MAD article:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml