First Time Out!!
You can get spring kits from Summit Racing or Jegs. You can also check your local parts store as some also carry the distributor spring kits. As far as capping the vacuum advance, when you are at WOT there should be no vacuum so the vacuum advance won't be doing anything. I would have it hooked up when you drive the car on the street.
Didn't mean to derail you thread earlier. Just thought you should be proud of your performance as you are matching my performance while being at a 42 cubic inch deficit. When you do purchase a converter, spend the extra money and get a good one. I wouldn't buy anything bigger then a 9.5" converter. The smaller converters gain efficiency and you can comfortably drive on the street with a much higher stall rating. If you mainly run the car at the strip, I would be looking for 3500-4000 stall as a minimum. Talk with the custom converter builders as they will be able to maximize the performance based on your engine specifications.
Have Fun!