Battery fried and more

Update: First of all, sincere thanks to everyone who responded.
Ok, so we thoroughly scrapped and cleaned all ground connections down to bare metal -Voltage regulator, alternator, etc.
When the car starts up the voltage meter would show the voltage climbing quickly up to 17-18v. Shut car off quickly.
We disconnected the field wires on the alternator and the battery would be steady at just over 12v. We discovered that this would also happen when you would hook up the positive field wire BUT NOT the negative field wire. When the neg field wire was disconnected, the battery would be stable around 12.3v.
To answer 67DART273: today we used a quality tester and the only wiring mods we have performed is bypassing the bulkhead by running a heavy gauge wire with appropriate sized fusible link from the alternator output stud directly to Bat (+) stud on starter relay.
So we are at a standstill right now.