I think it's a successful proven format. and I love "build" shows. to see the ingenuity that racers can have when pressed for time and money. Look at the Top Gear challenges, I'm glued to the TV whenever they do a cheap car challenge. so instead of just buying and challenging, have a build aspect too. That Idea my friend hits on all cylinders.

It has the Time crunch of Monster Garage
The Ingenuity of Junkyard wars.
Real tuning, and real racers.
The best part of Top Gear in my opinion.
autocross makes a great challenge too since any driver can win any day.
and insurance is cheap, and you don't need a ton of saftey gear to compete.

If you wanted to say.. In Tonight's episode, Vans, Station Wagons, Cars built by AMC, whatever. or Even give 2 teams a box stock car, and a budget and a time limit. "here is your 2006 Chevrolet Aveo, tomorow we autocross"