Pretty dumb buying it off Ebay and Paypal just to get it cheaper with no fees involved. That was your decision. Then come here and cry about it? You had everything at your disposal that would have protected you TWO TIMES OVER, both through Ebay and Paypal. You're your own worst enemy here.
Personally I agree with you if I had 15 grand laying around to spend on my car I'd get up with an engine builder and build one hell of an engine. My way exactly what I wanted.
Other than the cam card i dont see no huge problem with the transaction. I hate that the OP spent 15k and isnt happy with his purchase. I'm willing to bet the engine is fine tho. Most reputable companies Ebay or not isnt gonna have prices like that if its complete garbage and last long imo.