So first things first, the tank looks like a bow front tank. If it is you will not be able to drill the bottom. All bow front where made with tempered bottom glass.
If your are able to view the back as well I would suggest to put the overflow in the middle of one of the side's. Put in a 1 1/2" bulk head, you will have to put a 90 degree elbow on both side's of the bulk head. 1 going up on the inside of the tank and 1 going down on the outside of the tank. To keep you overflow small I would do a durso stand pipe. For the return I would come up the otherside also in the middle with a 1" bulkhead and 2 - 1/2" loc-lines inside the tank for the return.
Just my thoughts and ideas.
