Charging Voltage?

Start the car, get the battery "up" all accessories off, and the engine at a good fast idle. You should see somewhere between 13.5-14.5 Optimum is right at 13.8-14 depending on temperature. One good indicator of either battery problems or over voltage is constant "wet" battery and using lots of water. Use only pureified water in your battery.

One big problem nowadays is voltage drop across the harness, or ground link. To test this, first if you HAVE this problem, the voltage is normally OVER voltage.

Stab one meter probe directly onto the battery neg. post. Stab the other right onto the regulator mounting flange. Again, with engine running fast (simulate low-med cruise) you should see VERY low voltage, the lower the better. zero is perfect, anything over .2 (two tenths of a volt) is too much

Then check the "hot" harness side. Stab one probe right onto the battery positive post, the other as close as you can get to the regulator IGN terminal. Should be bare and accessable on a 69. Once again, zero perfect, over .2 is too much.

Either circuit being high indicates poor wiring or connections. On the ground side, try running an auxiliary ground, say at least no10 or 8, between the block and the regulator frame

On the hot side, check the path from the battery, starter relay, bulkhead connector, ammeter, ignition switch and connector, back OUT the switch and connector, back OUT the bulkhead. Somewhere in that path you have resistance causing a drop.