I forgot that this is a roller lifter small block. You need to use some CI4 oil in this engine and change it about every 500 miles or so until the clicking stops.

When you drain the oil, pull the plug while it's hot and let it drain for a long time.

I have an '88 Vette with the same engine and it was clicking when I got it. I only had to do about two hot oil and filter changes with Chevron Delo 400 until the clicking stopped. That was about 50,000 miles ago and it has been fine ever since.

Good luck,