In a large dry skillet toast guajillo and ancho chiles over medium, turning occasionally, until lightly toasted and fragrant, 3 to 4 minutes. Let chiles cool until easy to handle. Remove and discard stems and seeds. Transfer chiles to a large heatproof bowl; add enough boiling water to cover. Let stand 20 minutes. Drain, reserving ⅓ cup of the soaking liquid. In a blender combine soaked chiles and the reserved soaking liquid; cover and blend until smooth.
In a 5- to 6-qt. heavy pot cook beef over medium-high until browned, breaking up the meat as it cooks. 8 to 10 minutes. Using a slotted spoon, transfer beef to a bowl. Drain any fat from pot.
In the same pot cook bacon, stirring occasionally, until browned, 5 to 6 minutes. Add onions, bell peppers, serrano chiles, and garlic. Cook, stirring occasionally, until vegetables are tender, 7 minutes. Add pureed chiles; cook 3 minutes, stirring frequently. Add chili powder and cumin; cook and stir 1 minute. Add browned beef, tomatoes, and 1 cup water.
Bring to boiling; reduce heat. Simmer, uncovered, until chili is thickened, 30 minutes. Stir in lime juice and salt. If you like, serve with lime wedges and top with sour cream, cheddar, serranos, and/or cilantro.
