I have a '63 beetle, very original, down to the 6 volt generator and lights. I want to keep it that way, but am driving it quite a bit and the lights are mediocre at best. I am thinking about a conversion kit to go to 12 volts, but don't know whose kit is best.
Can anyone give me any advice on this project?
Thanks!

I have been told an 8 volt battery will make the lights brighter and start better in the cold,  think they have them at tractor supply

I think optima makes an 8 volt AND it's a sealed battery so it won't get acid on the floor pan and rot out anymore. If you go 8, consider the optima.

Other than that, I don't think the kit matters much. You'll need the generator, voltsge regulator, the bulbs (all turns, tails, brakes, dash, etc...), a resistor or 12v wiper motor, 12v horn, coil, maybe a flasher unit, and a radio-if it's currently 6v. The starter will last a while with the added voltage, but swapping out a 12volt unit isn't as easy because of the flywheel. It all depends on the engine and which way you want to go. If you put a 12volt flywheel on, you have to change the starter, the starter bushing and grind the transmission bell housing out a little ( or just run turn it over after installing it-steel> aluminum! It will self clearance). You can get by with the 6v as long as the starter holds up, don't crank it for long- wont need to because it will spin faster, but if it has trouble starting then you might be inclined to crank it longer than normal, which will kill the starter in time.

You have options. Read this http://www.airheadparts.com/6v-to-12v-conversion

If you change to a 12 volt generator (or alternator for that matter) you will have to change out the generator stand as well.  12 volt generators are a larger diameter.  If you want to keep the original stand and small diameter generator, I think there is a Porche 12 volt generator that will work . . . I've heard about it and seen pictures, but don't know any details.

A common misconception is that if you go to 12 volts you need to change the wiring harness to handle the extra voltage.  This isn't true. The 6 volt wiring harness has heavier guage wires than 12 volt.

I would stick with the 6 volt starter.  Like Nick said, as long as you keep your engine tuned, the starter will last for many, many years.

By the way, if you do this, don't toss out the 6 volt generator.  They make great 12 volt motors!  A friend of mine built a home-made winch for his trailer and powered it with a 6 volt generator.  It wasn't fast, but it would pull a non-rolling bus up on his trailer.

Keep your 6V starter. They will last a long time and another reason is that you can not use a 12 V "O"ring  flywheel on a 40hp engine due to the difference in the crankshaft where the flywheel is mounted. If you try to do this,it would be a total disaster.

Wow! I didn't expect so many responses...thanks for the advice, I have some practical knowledge now.
Last fall I replaced the generator with a rebuilt unit. I guess that would have been the perfect time to go 12 volt, but I am a hard-headed old cuss. I have cleaned terminals, and monkeyed with ground straps, but haven't improved things much. My left headlight is noticeably brighter than the right headlight and the voltage at that headlight is only about 5 volts. I'm running out of terminals to clean and am thinking about replacing all of the ground straps with new ones to see if that would help.
I like the 8 volt battery ideas, too, I remember seeing them in some of the older cars when I was a kid.
Thanks again for the help!

Is it an alternator?,  if not it should have a regulator

It is a alternator

Then it is internally regulated.

Unless its a 1 year only externally regulated alternator. These are the ones you always see on "turn key" motors at swap meets because they will cool/charge, but it won't work with the system in most vehicles. Every parts hoarder has 3 and can't give them away...

You can tell them apart by the wire hook ups. The internally regulated ones have a single threaded post/nut connector and a push on spade terminal. The externally regulated have a 3 wire plug and a threaded post/nut connector.

I ran an external one on my Baja because I had it and the regulator was cheap at autozone. It worked

Do a draw test,  unhook the positive cable and put a test light between the battery post and the cable,  if the light is bright you have a draw.  Unplug the alternator and see if the draw goes away, test light goes dim,  or take out fuses on at a time

You need to measure amps,  the simple way is a test light between the post and the cable with the battery disconnected, to get fancy you could use a clamp style amp meter over the cable with it connected