Here is a pic of my 55gal stand, I don't have any plans, but if you have any question I would be glad to hep out.
What I can tell you is that the bottom part is framed out with 2x4's, doubled up in each corner, cross braces added on the top and bottom, and what the stand sit's on is doubled up 3/4 plywood. Remember that the stand will be a little top heavy , so double up at the bottom so it won't tilt over on you.