Bring guajillo and morita chiles and 1½ cups water to a boil in a medium saucepan. Cover, remove from heat, and let sit 30 mins to allow chiles to soften.
Transfer chili/liquid to a blender. Add orange juice, achiote paste, garlic, lime juice, and salt. Purée until smooth, about 2 mins. Set aside 1 cup for basting.
Place chicken in a bowl and combine with sauce to marinade. Cover and chill at least 4 hrs and up to overnight.
Thread alternating pineapple pieces and chicken meat onto skewers.
Grill skewers over medium-high heat about 5 mins per side. Baste often with reserve marinade.
Serve with warm tortillas and taco fixings.