Here's what the smart local engine builder, who's engines you see up front does.
Your at the track every week and you have seen a lot of kids grow up racing. Your also able to pick out the kid who seems to have a little bit of talent and who's parents likely will provide them with good equipment. What you do is when you see the kid mature and become maybe a little better then other kids or progress faster, you cut the parents a deal on an engine. The parents save a buck and you then have your engine on the shiniest, most well prepared kart on the track, which also has a competent possibly up and coming driver. For the rest of the racers that combination is what they will be chasing and the rest of the racers will feel they will also have to have the same engine. The truth of the matter is the front running kart would have been the front running kart, no matter who's engine is on it. The slick smart local engine builder was able to put his engine on the winning kart, the winning kart did not go out and seek the engine builder. What follows is if the engine builder gets his engine on enough already quality stuff and becomes a national engine builder. I'd bet what ever name you choose and relate to as the good stuff, followed that sequence to success. General you won't get offered house motors or a deal on price, until after you beat or about to beat other house motors.
When your buying a race engine, here's another thing to consider. The engine builder is not always going to give you the best engine he can produce, but they will still charge the price of the best they can produce. The engine builder is going to give you an engine, built to what they think you can handle. If you don't have the knowledge to use his best stuff, it will not only not perform well for you, it will most likely fail and you'll blame the engine builder for your lack of skill.