I used Whitepost for my double bore TR2 Lockheed master cylinder on the TR2 and the Doretti, and the rebore (with stainless, I think?) has been fine. An ownership change occurred in the last 3-5 years ar Whitepost, I believe, but they did really nice work for me and backed it up with a lifetime guaranty. I would recommend a quality rebuild of an original part rather than a cheaper newly manufactured part. There have been problems with classic gold stuff in the past, and its hard to keep track of what quality standards are used. I don't think the rebuild or reboring is rocket science, so maybe Apple can do as well as White Post.
Dan