1968 Pontiac Bonneville charging system question

I recently replaced the battery, alternator, and voltage regulator hoping it would solve my problem... It hasn't. When I start the car, every light inside and out (when turned on) pulsates. The battery is not charging. but so far the car turns over fine. I thought it could be the ground strap to the engine, but it's connected. I also cleaned the terminals to the battery & checked the cables/wires where I could throughout the system. Nothing seems to be burn't or frayed. I'm sure it's something simple, right? Please help! -Jake