If there were 2 things i would not suggest using from ebay it would be a turbo and the wastegate. You can get away with ebay intercooler/piping and cast manifold, but i wouldn't take any chances. Personally, id sell the turbo on ebay or craigslist and buy a real one from Precision, Garrett, Master power, or Turbonetics. Alslo, i think you might have better luck with a used tial over a new "ebay" branded one. Just my experiences.
Good luck on your build.