The Crown Royal International Race of Champions (IROC) is heavy into preparations leading up to the $1 million dollar season finale, which will take place Saturday after the Aaron¿s 312 Busch Series race at Atlanta Motor Speedway. During Saturday¿s race, 12 drivers from different disciplines of racing will drive identically prepared machines, battling for a record Crown Royal IROC purse in a race unlike any other in America. In order to have 12 identically prepared cars for those 12 drivers ¿ Ryan Newman, Matt Kenseth, Jimmie Johnson, Kurt Busch, Kevin Harvick, Danny Lasoski, Steve Kinser, Helio Castroneves, Scott Sharp, Scott Dixon, JJ Yeley and Travis Kvapil ¿ IROC has been testing diligently at Atlanta since Saturday. IROC Director of Public Relations George Signore explained the five-day test sessions, and everything the series needed to accomplish to be race-ready. ¿We bring 17 cars with us. Four of the 17 are just for driver practice, and are the ¿test mules¿ with drivers Dave Marcis and Jim and Jay Sauter doing all the set up work,¿ Signore said. ¿The four ¿practice cars¿, as we call them, are used to arrive at a final chassis set up and are also used by the competitors for driver practice. The series competitors only drive the practice cars ¿ they never drive their assigned race car until the race.¿ Signore explained that the other 13 race cars are set up and qualified, so that there is one per competitor plus a spare. In order to ensure that all are identically set up, the test drivers will start ¿speed runs¿: they will speed each car up, or down, and work on any differences in handling characteristics until the cars are as close as possible. ¿Each car has a logbook and is assigned a crewmember that will note all the lap times and driver comments, if any, and will log all of the work done to the car,¿ Signore said. ¿The log is a detailed diary. By Tuesday, we¿ll have matched up all 12 race cars, with the 13th being designated the spare car.¿ After that, IROC holds a drawing to match up drivers to chassis numbers and crew members to drivers. Once the drawings are complete, a crew of graphic experts will apply the colors, names and numbers, which will take two full days to do all 12 race cars.   DOUBLE DUTY: A slew of NASCAR drivers will be doing double duty this weekend at Atlanta Motor Speedway, running both Saturday¿s Aaron¿s 312 Busch race and Sunday¿s Bass Pro Shops MBNA 500. The drivers expected to start in both races include: Tony Stewart, Kevin Harvick, Matt Kenseth, Kenny Wallace, Michael Waltrip, Casey Mears, Kasey Kahne, Kyle Busch, Martin Truex Jr., Mark Martin, Jamie McMurray, Kyle Busch, Greg Biffle, Johnny Sauter and Robby Gordon. Another driver pulling double duty this weekend is Peachtree City (Ga.) native Reed Sorenson, who will compete in Friday¿s World Financial Group 150 and Saturday¿s Aaron¿s 312. And one driver will be competing in all three races: Mark Martin will return to his ASA roots for Friday¿s World Financial Group 150, then try to up his AMS-record Busch win total in Saturday¿s Aaron¿s 312, then finish up the weekend in the Bass Pro Shops MBNA 500 on Sunday. NEW SPONSOR FOR #50: Arnold Motorsports announced that Atlanta-based U.S. Micro Corporation will be the primary sponsor of the No. 50 Arnold Motorsports Dodge for the Bass Pro Shops MBNA 500 at Atlanta Motor Speedway this weekend with Todd Bodine behind the wheel. U.S. Micro Corporation, a national computer and technology asset disposal company, became an associate sponsor for the No. 50 team three weeks ago. ¿With our company being based in the Atlanta area, having an increased direct involvement in this event through sponsorship of the No. 50 NASCAR Nextel Cup car allows us the opportunity to entertain clients and reward our employees at a high-profile event with national exposure,¿ said Jim Kegley, U.S. Micro Corporation president. Team owner Don Arnold said the car will have the same ¿lucky¿ paint scheme as the No. 30 Toyota truck. Of the six NASCAR Craftsman Truck Series races Bodine has driven for the No. 30 Germain Arnold Racing team, he has posted five top10s, including back-to-back wins at Texas and California.