Are you saying the belly flaps, side ribbons or the white side which is called fluke belly when its cut in strips?
Me, I fry the belly flaps from every fish, codfish is the best. As you said, high fat content.
people waste the best part fo any fish. Cook your fish whole, head on and eat the meat out of the head and cheeks.
Big fish, steam the heads, pick them and make chowder.
Don't mangle the roe either. Big codfish roe gets par-boiled 'til its firm them sliced, floured and fried. Small roe from small cod, mackerel get floured & fried. Fluke & flounder roe stay in the fish when gutted and eaten with the fired or baked fish.
Most people are looking for fillet cut like Gorton's and haven't a clue asto what they are doing.
Growing up, I didn't have a filleted fish until I was out of the house & on my own.