You can reuse them, no problem. All you have to do is flush the components your reusing. They have a solvent at good auto stores you use to flush the components with, they must be clean before recharging. You need a new drier and a new expansion valve. New hoses would be a good idea especially if your going with R134A, I don't think that the 76 hoses are compatible, you need "Barrier" type hoses.