Heat oil to 375 degrees in a dutch oven deep enough to completely cover shrimp and oysters. Place 1 cup of flour in a bowl and add House seasoning. In another bowl, beat 3 eggs and add hot sauce. Dredge shrimp in egg mixture and flour mixture and drop into hot oil one at a time. Fry until light brown (do not over cook). Lightly flour oysters and drop one at a time into hot oil. Fry until golden brown. To assemble sandwich, spread both insides of bread with tartar sauce. On the bottom piece, place shredded lettuce and sliced tomato. Add salt, pepper and garlic powder to taste. Place oysters on top of tomato. Place another layer of shredded lettuce and then place shrimp on top. Top that with bread and toothpick to hold sandwich together.
In a bowl, combine chopped onion, pickle, mayonnaise, and House Seasoning and mix well.