We race CARS, so it only makes sense, to me anyway, that the car needs to be as good as the engine, trans, etc...
So if you don't pay alot of attention to things that help mph like front end alignment, tires, pressure, oil viscosity, brake drag, and such your not going to get all you can. It's easy to say on the net that your cars mph is xxx but what it takes to achieve that is probably not so easy.

Truth is different dyno brands will show different #'s...hell same brand dyno's can show different #'s depending on so many things. Just like flow benches. In the end, what the car runs is also dependant on many many things.
I see alot of customers that want a certain mph or e.t. but may not be willing to work on the car until they get it...if they buy an engine they figure it's the engine builders responsibility to make their car meet their expectations.