[gtofreek]

Sounds like the regulator but make sure it has a good ground because a bad ground to the regulator will cause it to overcharge also. I run a test ground wire from the battery to the regulator base to test for this. Unplug the regulator and make sure it quits charging. If it is still charging at 17 + volts with the regulator unplugged, then it sounds like you have the alternator field wire melted into the battery wire. Probably just the regulator though.

You can double check the wiring at the regulator plug by unplugging the regulator and checking the wires for power with a test light. Two wires on one end should be hot with the key on and two at the other end should have no power on them until the regulator is plugged in. The wiring arrangement in the regulator plug is from one end to the other,
1. ignition wire from idiot light.
2. hot wire from battery.
3. stator wire from alternator[used to backfeed power to turn off the idiot light].
4. field wire[this is a blue wire that the regulator uses to control the alternator. The regulator feeds power out this wire to the alternators field terminal which in turn causes the alternator to charge.]
These numbers above are strickly for this post and do not reflect numbers that may be on your regulator.

Sorry about the fine details but sometimes it helps to know whats what so you can make a good diagnosis without wasting money on parts you may not need.