Preheat broiler.
Use 1/3 cup oil to brush both sides of each slice of bread. Place the bread on a broiler tray and grill for about 2 minutes per side or until each side is golden. (Alternatively, use an outdoor grill.)
Combine shrimp, beans, tomatoes, and basil in a nonreactive bowl. Whisk together remaining oil, vinegar, garlic sugar, salt, and pepper, and pour over shrimp. Cover and allow to marinate for 1 hour.
Line a serving platter with the grilled bread. Pour shrimp salad over the top and serve immediately.
Serves 6