It didn’t take long for the Cash for Clunkers voucher idea to go from concept to reality. It was just earlier this week that Rep. Candice Miller (R-Mich) and Rep. Fred Upton (R-Mich), contacted the Secretary of Transportation, Ray LaHood, petitioning him to let people looking to take advantage of the Cash for Clunkers program, to use vouchers to order cars from manufacturers.

Yesterday, the Obama Administration OK’d car purchasers to order vehicles that aren’t in stock at a dealership using a voucher. This will let people be fully able to pick the car that they want without having to miss out on the full Cash for Clunkers rebate.

Dealerships had been having a hard time keeping up their supply with all the demand that’s been created by the success of the Cash for Clunkers program. LaHood said the changes will expand choices available to buyers while keeping up production for the auto manufacturers. He went on to describe the program as being, “wildly successful.”

The Transportation Department said Thursday that consumers who want to purchase a new car not yet on the lot at a dealership can still take advantage of the CARS rebate but wait for their new car to arrive from the factory. LaHood said the changes will expand buyers’ choices and keep production lines running. He said it is a “wildly successful program.”

This list we link to below is based on the requirements set forth in the Consumer Assistance to Recycle and Save Act of 2009 (commonly known as the “Cash for Clunkers Act”) that was enacted on June 24, 2009, as well as the published regulations issued by the National Highway Traffic Safety Administration (“NHTSA”) on July 24, 2009.

The list is comprised of models that have an average fuel economy of 18 mpg or less and for which at least one of the styles of that vehicle has a current average national trade-in True Market Value price (unadjusted for options or color and assuming “clean” vehicle condition and average mileage of 12,000 per year) of $4,500 or less.

Check out the full list here.

As we are on the verge of seeing the Obama Administration’s Cash for Clunkers program on the verge of becoming a reality, we’re now starting to hear more dissenting voices that warn that the program might not jump start U.S. auto sales like they hoped.

Arguably, the problem comes from it seeing so many changes since it’s original introduction. It’s current form was recently analyzed by four experts at Automotive News who estimate that the bill will only result in new car sales of 70,000 – 200,000.

They base this estimate on three main issues surrounding the Cash for Clunkers program.

The first issue being that the limit of 18mpg doesn’t encompass enough vehicles. The second being that clunkers will only be able to be turned in between July 1 and November 1. And finally, they point out that most people who could afford a new car would probably already have bought one and that even with the maximum discount of $4,500 it probably still makes more sense to buy a used car.

One thing is for sure though, at very least we will see some polluting clunkers pulled off the road and replaced with newer, cleaner vehicles. Whether or not it manages to give a the struggling US auto industry a boost remains to be seen.