I've heard our esteemed judges bemoan "race car copies" many times. They absolutely hate to see most of the classics, such as the infamous Gulf GT40 theme.
Better to think further outside of the box.
Make your Jag look like an Olds Silhouette minivan... then you might be onto a winning theme.
The powers that be don't want to see a track full of Lemons that look like "race cars". They want to see a track full of Lemons that evoke a "what the fuck is that, and why is it on a racetrack?" response. If the answer to that question is "I'm not sure what it is, but it's cool in a horrible kind of way, and look... it actually passed somebody!", so much the better.
Lemons South 2008 - Fail, Lemons South Spring 2009 - Fail, Lemons Detroit(ish) 2008 - Fail, Lemons South Fall 2009 - Fail, Lamest Day 2009 - Fail, Miami 2010 (Chump) - 2nd!, Sebring 2010 (Chump) - Fail, Cuba 2010 - Crew Chief, Roebling 2011 (Chump) - 8th!, Sebring 2011(Chump) - 19th!