He has coarse, longish white hair and he sheds a lot. He has the "cracked" eye blue and brown on his left eye. He is very spotted. His head is large and kinda squarish like a pit, but the spots and cracked eye say Catahoula to me. Thoughts?
Lots of dogs are spotted, especially at that modest level, and can have cracked eyes. If you knew for a fact he was part Catahoula I wouldn't doubt you because I can see some of the proposed resemblance (it has to do with head structure primarily and has nothing to do with his coloring, which he could have gotten any number of ways), but you should probably have asked why the rescue labelled him Lab/Husky... especially since his head isn't square to the point that it absolutely screams bully to me. Many Labs also have very square heads.
I don't think the answer is as straightforward as pure Lab/pure Husky because his fur seems short for that, but I don't think mostly Lab/Husky is necessarily wrong, either. I could see him being part Pit or part Catahoula, but unless he came from an area where Catahoulas are thick Catahoula is rarely a probable guess. I don't think he's straightforwardly half Pit / half Catahoula, either. Those mixes tend essentially to look like Pits. I could see Pit / Husky. Both Pitties and Huskies are pretty commonly piebald, so the spotting wouldn't be a surprise with a mix like that.
We have a good amount of Catahoulas down here and if I has to guess I'd say lab pit mix. The husky was probably thrown in because 1) if it has different eyes it must be a husky to most shelters and 2) I'm not sure about the insurance laws in your state but I know most rescues aren't allowed to have "aggressive" breeds such as pit bulls due to insurance, so since the pit isn't incredibly obvious he was probably labeled lab/husky to keel him legal.
Handsome boy either way! Gotta love the different colored eyes.