I am doing some work on my leaky rear end. I have a hole in my pinion carrier not sure if it is a problem. Might be a question for Royce. If if is a problem where can I get another? 68 XR7-G 302 C-4 trans.
Cast in oil drain return for the front pinion bearing. Normal, not an issue
The main question is…did you locate the leak location prior to disassembly? Pinion support Oring leak, seal leak at seal or outer seal 
interface to pinion support, pinion nut from no slinger or overfull?