Does the old mod that made the default ship items breakable still work or would it need to be remade for the new shipworld files?
Depends on which mod you are referring to. However, if you would like to make them destructible yourself, you'll have to modify or patch into the blockkey.config files for each race's ship and change every instance of Code: "unbreakable" : true to Code: "unbreakable" : false (or remove it entirely, but patching is more friendly to compatibility)
