I remember when I was selecting a builder. I wish I had listened to any one of the recommendations I got on here when selecting a builder. Best advice I can give is using someone who is reputable for quadzilla engines and someone who will take the time to talk to you about the engine and desired work before you commit and send your stuff to then. If someone isn't willing to communicate to earn your business you can be damned sure the communication won't get better once you've sent your stuff and committed to a price. Skilled labor isn't cheap and cheap labor isn't skilled, you get what you pay for. It's cheaper to pay more to have something done right the first time then it is to pay to have it done twice.