That carrier is in terrible condition. I'd want to start with a complete center housing from a donor rear end and scrap the entire center section you've got there. There's no telling how much load has been put on the housing casting, or how many stress cracks there might be in it, just waiting to destroy all your hard work and expense of a rebuild job. These rear ends aren't that scarce, as the same assembly was used for a range of several years from the mid-1950's to early 60's.
Jerry
