Sorry its taken me a while to get to this. Interior is roughly 59x22x30. As i said it can get a little cramped in there. i built my control board to sit front to back to try to maximize the space a little more and figured it would allow for more room but after installing it, really didnt give me what i wanted but its functional.
Here is a pic of the sump area which is a bit of a mess right now. If it wasnt for the 10G ATO i would have a little more room.
Above you can see the control board. It slides out but limited on how far to left it could go since the hinges are in the way.
If you have any other questions just let me know.