C36's have done off shore work, and still do in a lot of cases. That said, WHY take a great coastal cruiser and try to convert her for the off chance of going off shore?
Define off shore first, and if you are going to do true passages, get a different boat. The boat will take the beating of a passage if it is in good shape to begin with. However, tankage is not adequate for long passages, and if you add lots of tankage you will lose the little bit of storage you have. Buy a boat that you can invest in for the future. There are bluewater boats available in your price range, that with work can last well into the future. The dollars you invest to make the C36 a passage maker will actually devalue her.