Thaw shrimp and squid, if frozen. Peel and devein shrimp, leaving tails intact. Rinse shrimp and squid; pat dry with paper towels. Cut squid into thin rings. Drain minced clams, reserving liquid. Cover and refrigerate shrimp, squid, clams and reserved liquid until ready to use
Scrub the mussels and littleneck clams and under cold running water. Using your fingers, pull out the beards that are visible between the mussel shells; discard. In a very large bowl, combine 3 quarts of the water and 3 tablespoons of the salt. Add mussels and clams and soak for 15 minutes. Drain and rinse thoroughly; drain. Repeat two more times. Drain and rinse mussels and clams thoroughly.
Meanwhile, cook pasta according to package directions. Drain; keep warm.
In a 6- to 8-quart Dutch oven, heat oil over medium-high heat. Add the shrimp, squid, and minced clams. Cook and stir about 3 minutes or until shrimp are opaque. Remove shrimp, squid, and clams; set aside.
Remove pan from heat. Add wine and garlic to Dutch oven. Return to heat. Bring to boiling; reduce heat and simmer, uncovered, 5 minutes or until reduced by half (measures about 1/2 cup). Add mussels, littleneck clams, the reserved minced clam liquid, the clam juice and crushed red pepper. Bring to boiling; reduce heat. Cook, covered, for 5 to 9 minutes or until mussels and littleneck clams open, discarding any unopened shells. Stir in drained pasta, shrimp mixture and pasta sauce; mix well. Simmer, covered, for 5 to 10 minutes or until mixture is heated through.
To serve, spoon pasta mixture on a large serving platter, making sure most of the shellfish is on top. Sprinkle with parsley.
*If you cannot find mussels in the grocery store, you can substitute extra calms.