In a large mixing bowl, combine the olives, tomatoes, artichoke hearts, mozzarella, olive oil, lemon juice and zest, truffle oil, pepperoncini peppers and liquid and garlic. Toss, season with salt and pepper and set aside to allow the flavors to marry, about 1 hour.
Preheat a grill to medium high. Brush each slice of bread with olive oil. Using tongs, transfer the bread to the grill, oiled side down. Grill until crispy and grill marks appear, turning once, about 3 minutes per side. Transfer the grilled bread to a serving platter.
Top each bread slice with half a slice of prosciutto and 1 heaping tablespoon of the antipasti mixture. Drizzle with more truffle oil to finish, if desired, and sprinkle with basil.