Terry,
As for amps, you should be more concerned with wattage if you're considering using the white wire for lights. It has been experimented with countless times and the results have always shown that anything much over 2.5 to 3 watts will adversely effect ignition performance. Reducing the spark plug gap by a few thousanths can help a little but not much. If I had my way the white wire would not be there. An on board battery to power lights, and in some cases a tire driven or hub generator is a far better option than trying to use that trouble prone white wire. Good luck and just wait; you're going to get a lot more advice and if you use the search feature (keyword: White Wire) you'll have lots to read on the subject.
Tom