In the car business this year, financial engineers may be just as important as their mechanical counterparts. As plummeting emerging-market currencies broadside major automakers, the company that has the most finely tuned policies for pricing and hedging exchange-rate risk stands to win big or at least lose the least. The challenges were abundantly clear in the past few days, as Ford Motor and General Motors talked about their struggles in South America -- specifically Argentina and Venezuela. Last year, inflation in Venezuela hit a blistering 56%, outpacing every economy in the world, while prices surged 28% in Argentina. On top of currency instability, economic growth is slowing down drastically in both countries. That's made for some cautious consumers. Both companies are moving fewer vehicles in the region.