Combine 1 1/2 tablespoons of the lime juice, the lemon juice, peppercorns and olive oil in a small container. Add the shrimp and scallops and marinate, refrigerated, for one hour. Drain the seafood and discard the marinade.
Prepare the salt block for high-heat direct cooking (500 to 600 degrees F.) and cook the shrimp and scallops for two minutes. Turn and cook another two to three minutes or until done. Using tongs remove the shrimp and scallops from the block and divide the shrimp and scallops onto two warmed serving plates.
Garnish the seafood with the lime and lemon peel and drizzle with the remaining lime juice. Sprinkle with additional crushed peppercorns if desired.