Mod resource pack

I am currently playing with the mod Ice and fire:spellbooks which is a compat between ice and fire and iron's spells. This mod add a few helmets that have a 3d model which quite frankly we just don't like. I was hoping to change that with a resourcepack. I was hoping to just change them to something that uses the default minecraft helmet model and to retexture that as tiny crowns or something like that. How would I go about it?
I've located the .json files in models and in geo and both the .png files in textures. I'm assuming I need new textures but also need to change the model they're applied to and idk how to do that.