[wwest]

You probably have a voltage drop somewhere between the alternator/regulator all the way in the back of the car and the battery all the way at the front. Check the + connection at the starter solenoid. Also be sure the battery posts and connections are cleaned and burnished and check that the battery ground cable at the chaisis end is well grounded/connected.

Check/read the voltage across the battery terminals vs the voltage at the rear of the car while the engine is running.