Well, no offense intended. Having worked as a Mechanic on consumer vehicles in the past, and seeing some of the rebuilt engines put out by various rebuilt engine companies, I think most accomplished Techs could build a better engine with better components, for less money.
That's what I should have said in the first place.
As far as places that build a good 5VZ-FE, I have heard (no personal experience) good things about this place:
Toyota Performance Parts | LCEPerformance.com
Just looking around the site, they definitely aren't the cheapest, though.
Good luck.