small block ticking issues

Most likely, whoever rebuilt it forgot the oil galley plug that goes right behind the pil pump drive gear. I've seen that one a few times. Pull the distributor, pull the oil pump drive and look down in there with a flashlight and see if there is an oil galley plug or not. My guess is that there isn't one. If there isn't, it's a pain to install with the engine assembled, but it can be done if you're careful.