Lay the chunks of pork in one or more large tubs (I've used vegetable bins from my "extra" refrigerator in the basement as well as roasting pans). Mix together the lime juice and salt. Smear the mixture on all sides of each piece of pork, cover and refrigerate for several hours.
Set up a turkey fryer: fill with oil to the level marked on the turkey fryer for a 16- to 18-pound turkey, attach the thermometer (I always test mine in boiling water to insure that it's accurate), and, if your model has one, slide in the raised perforated plate that will keep the meat from resting on the bottom of the pan. Heat over medium-high heat until the lard or oil reaches about 275 degrees. Carefully lower in the pieces of pork, but none of the juice that may have collected around them. (Add the bacon, if you're using it.) Adjust the heat to between medium and medium-low. After the oil's initial frenzy of having received the moist pork, it should settle into what looks like a brisk simmer when you have the temperature right. You'll notice, too, that the temperature will have dropped to just above 212 degrees - the boiling point of water - indicating that the meat is literally simmering in the oil. Using a pair of long tongs or one of those large Chinese wire strainer/skimmers, gently move the pieces of meat every 10 minutes or so.
In about 1 1/4 hours, the meat should be completely tender, but not falling a part - start checking it at about 1 hour. When it is completely tender - meaning you can pretty easily pull it away from the bone - remove it to a large paper towel-lined pan. The carnitas are ready to eat - though they may not be as brown as you're expecting. (They will, however, take on more of a golden color as they begin to cool.) To give them a richly browned exterior, raise the heat under the lard or oil and let the temperature rise to 325 degrees. A piece at a time, lower the meat into the oil and let brown - it'll only take 45 seconds to a minute. Drain on paper towels and keep warm in a low oven until you're ready to serve. (Though I use the bacon mostly for flavor, I like to brown it with the other pieces of meat and chop it up for my guests to enjoy.) You may wish to pull the meat off the bones in large chunks, removing as much fat as you like in the process. Set out for your guests to make soft tacos with warm corn tortillas, guacamole, salsa, and, if you wish, beans.