There are two holes for 1" bulkheads at one end of the bottom and one hole at the other end of the 40 breeder. This tank is sitting on a rack that I built from 4x4's and served as my mixing tank. These holes were plumbed so that I could easily turn a valve to do my water changes and also another valve was used so that I could get RODI water into buckets if needed.
The 75 is drilled with three 1" bulkhead fittings at one end of the tank. These holes are down low on the end as these were return pump connections to my tanks.
unfortunately, I do not have pics and cannot get any right away. My ex-wife lives in this house and simply wishes that I get these sold and out of the house. I will ask her to take some photos and provide them, but I suspect that it will not be anytime soon...probably next week.
If you typed 75 in your message and actually meant 65, then that one is drilled with two 1" bulkheads through the bottom, near the backside of the tank. Again....no photos right now. There is also a hole drilled in the backside near the top that a 1" bulkhead could be mounted, but I put an acrylic plate over that hole so that I could mount a float valve. This tank was used for my RODI storage tank.