rear distribution block and vent bolt?

I'm swapping an a-body 8.75 rear to replace my 7.25 rear. I realize I need to replace the rear brake lines to fit the new rear, but can I use the old distribution block? It currently doesn't seem to have a vent bolt, but just a bolt. If I replace the bolt with a vent bolt, will it just bolt in properly, or do I need to get a new block too? I believe the vent bolt for the 8.75 is 7/16x20, but I'm not sure about the old bolt.