My 89 chevy caprice with a 305 is leaking antifreeze from the back of my firewall (passenger side) onto the exhaust pipe. It is dripping onto the exhaust just past where the two exhaust pipes come together from each side to form a single exhaust pipe.

Check the heater control valve and the hoses where they go into the firewall. If the leak is not there, then the most likely problem is a leaking heater core. You need to look carefully to find the source of the leak before you can repair it. Use a flashlight, mirror or whatever is necessary to do that. If it is a hose, use extreme care removing it from the heater core connection. best to cut it off with a razor blade. If it is the heater core,most times it will make the passenger side rug wet. If it is the core, it isn't an easy job and I'd consider either getting a haynes or chilton manual to guide you, or, have a good shop do the work.
good luck

Could be,,,,back off intake to head ,,or u have a soft plug rotted out,,ck out soft pug next to starter,,,

It is either a heater hose connected to the intake manifold or it is the actual heater core. Look behind the carb at the hoses going from the manifold to the heater assembly and wiggle them around while the car is running and look and listen for the leak.