Spinach Stuffed Shells

I really like these but haven't made them in a long time. I haven't found any gluten free shells. If you find them...let a girl know! This recipe is from Southern Living

Ingredients:
18 jumbo shells
20 oz chopped frozen spinach, thaw
1 lb ground beef
1/4 t nutmeg
1/2 t salt, separated
1/2 t pepper, separated
16 oz marinara sauce (I love Newman's Own)
16 oz ricotta
1 egg
1/2 c Parmesan

Directions:
Cook pasta according to directions
Drain spinach well
Cook ground beef, drain and return to skillet
Stir in nutmeg, 1/4 t salt, 1/4 t pepper, and sauce
Stir together ricotta, egg, Parmesan, 1/4 salt, 1/4 pepper in a bowl - spoon into shells
Spread 1/2 sauce in a lightly greased 13x9 baking dish
Arrange shells over sauce
Pour remaining sauce over shells
Bake, covered at 350 for 30 minutes

*Stuffed shells may be frozen up to 1 month before baking - thaw in fridge overnight - let stand at room temp for 30 minutes then bake as directed