I notice that at night, the headlights are brighter with higher rpm. The voltmeter says that I have a good charge at the battery (which is new. Is this a regulator problem or a weak alternator.

Measure the voltage at the battery and then measure it at the headlamp connector. Most likely you will find the voltage lower at the headlamp connector because you are pulling alot of power thru the small power wiring that is ran from the battery to the horn relay, and then from the horn relay to the fuse box, and then from the fuse box back to the front headlamps.
Solution is to run a new Power Post near the horn relay, run a nice 8 gauge from the battery to this power post, and then run headlamp relays off the power post. Alternative is to just go with headlamp relays off the horn relay which will probably solve your problem as well but I like beefing the electrical up myself.
MadElectrical.com Headlamp relays (two)
http://69camaro.nextmill.net/electrical/DSCN0327_sm.JPG

Greetings,

Just converted my '68 Camaro over to the "New System" which I purchased from Mark at M.A.D. Electrical and wow what a difference I see in my headlight brightness! I would HIGHLY recommend the “New System” at M.A.D. Electrical! Also check out his article on brighter headlights http://www.madelectrical.com/electricaltech/brighter-headlights.shtml

graemlins/hurray.gif

Thanks for the tip. MadElectrical had a great article. I'll be placing my order this week.