Aston Martin has carried the flag for Ford in ALMS for the past several years...pretty damn well in fact. Lends an international bent for the series, and allows them to run in Europe with modifications. Shelby's a good label, but having a DBR1-colored Aston Martin and numbering it "007" ain't assactly a bad marketing move (though its teammate 009 was the better runner).
Saleen's running in GT-1 as well, as does Panoz. So, Ford is represented more than most.
But with Ford shedding its high-end stuff, maybe the door does open for a Shelby racing team...although a Ford GT might make more sense. It would harken back to Shelby running one of the GT40 teams.