Nice score. I have that shelving on the West end of my shop. I used 3/4" plywood to make the shelves. The lower ones with the heaviest loads got some 2X4 bracing underneath. Lighter stuff goes on top.
I'm sure you have already done this, but make sure you anchor those shelves to the wall. We had a man killed at a job I had as a kid(wasn't there when it happened) when he started climbing up on them to get an item off of a higher shelf. They weren't anchored to the floor nor the shelves.