Building it yourself (with a mechanic anyway) will be more expensive but youll know nothing was done half-assed or wrong and you can select all the best componenets to build the best motor for your application. I would trust LCE to do a good job putting a motor together, its what they do. Ebay is a little less trustworthy, epsecially if its a used motor.
So thats the order I would do it in if I had the money available.