i HATE phantoms i mostly play manhunt you know and i need a lot of time to do it then THOSE GUYS spawn and are everywhere THEY CAN GET INTO CAVES | also, dream never knew this cuz hes low skill but glow squids are so useful spamming F3+A makes you see mobs and they are the only way to detect the paradise (underwater caves cuz no mobs to fight and you just use a door to avoid drowning)
You just place the model in assets/minecraft/models/block and the texture in assets/minecraft/textures/block for a resource pack. I have no idea where to put this in a mod, but I'm pretty sure it should follow the same path
actually, I'm pretty sure data packs and resource packs have the same structure, so you might be able to include an "assets" folder in a datapack or a "data" folder in a resource pack, but I dont know if the game will be able to read both