Fry 4 slices of bacon until crisp, drain on paper towel, then crumble bacon.
Remove tomato navel, core tomatoes, scoop out inside centers and chop finely.
Sprinkle the insides of the tomatoes with 1/2 teaspoon of the salt. Turn the tomatoes upside down on paper towels to drain, then place in refrigerator and chill.
Add onion, diced green chilies, lemon juice, and the remaining salt to the chopped tomato. Mix and chill.
When it is time to serve the salad, mash the avocado mixture and stir into the tomato mixture. Do not allow to stand, or the avocados will darken.
Place the tomatoes on the bed of lettuce. Fill tomatoes with guacamole, and top them with the crumbled bacon.