when I drive my car at night the dash board lights are dim at idle but bright when I pick up speed is it the battery or alt. did a 69 come with a top mount battery or side mount
I'd have to say the alternator. But, Check belts, pulley & all charging elements including the battery. If all checks out you can run these series of tests on your alternator;
http://www.wikihow.com/Check-an-Alternator
Batteries;
http://www.camaros.org/underhood.shtml#Batteries
while the car is running discionnect the battery cable the alternator should keep the car running late production cars mine is Oct 69 and has side terminals
Also check your voltage regulator.
VT