Slant six over heated and now will not keep an idle.

Wait a minute, what amperage is your new alternator? Stock alternator was I believe 35 Amps, anything over on a stock wiring harness and you'll have all types of problems. Can you attach a picture or tell me exactly what red wire melted? Carb Repair is really simple for a one barrel. Download or buy a factory service manual to give you instructions for servicing the entire car.