My brake  distribution block was leaking from the weep hole so I found a kit to rebuild it.  I did the rebuild and it still leaks but much slower. So I bought another kit .and an original valve to rebuild. Hope this fixes the problem.  Has anyone any experience with these distribution blocks and what the purpose of the weep hole is?  I was told it is just to let you know the seal is bad in the valve.  I was also told that the new blocks being sold are junk and to stick with originals. But having no experience I can't speak to it.  I bought my kit from Muscle Car Research, they are the only source for a rebuild kit.  Any information on this would be appreciated.

I had replaced the one on my '75 a few years ago with a new one, and it seems to work fine.

I bought the new one from one of the Corvette vendors online.

This may be off topic, but I'm having difficulty centering mine. I have good front brakes, but none on back. It was bled by gravity. Not sure why it's acting like it is. The unit is new. Any advice?

Give your brake pedal a fast hard stomp a couple of times. That should center the valve.  If it is not centered your brake light should be on. 

Gary