Unroll the pancetta slices and cut them crosswise into 1-inch lengths. In a large skillet, cook the pancetta over medium heat until it renders much of its fat and the pancetta begins to get crisp, about 20 minutes. Drain the pancetta in a sieve placed over a heat-proof measuring pitcher. Add olive oil to the pancetta fat, as needed, to total 1 cup.
For the dressing:
Return the fat to the skillet and place over high heat. Add the garlic and cook until it begins to brown, 1 to 2 minutes. Remove the skillet from the heat and let cool to room temperature. When cool, add red wine vinegar and salt and pepper, to taste. (Taste before adding salt as the pancetta is already heavily salted.) Mix in 1/2 of the chopped basil. Set aside.
For the salad:
Preheat the oven to 500 degrees F.
Place the slices of bread in a single layer on a rimmed baking sheet and toast in the oven until golden brown and just beginning to crisp, about 6 minutes. (You can also toast the bread on a stove-top gas grill.) Remove from the oven and lightly brush the bread slices on both sides with olive oil, then season lightly with salt.
To serve, arrange a row of lettuce down the center of each plate. Slice the tomatoes 1/2-inch thick and arrange on 1 side of the lettuce. Cut each bruschetta on the diagonal into 2 or 3 pieces, and arrange the pieces on the side of the lettuce. Place some pancetta in the center of each plate. Spoon an equal amount of the dressing over each plate. Sprinkle with remaining basil and serve at once.