All weight is said to go to the corners. ?
Adding a 2x8 to the back the 48 inch length and cutting 2 pieces to support it at stand height from the floor would work for the 75 IMO
. Not seen since in the back no biggy.A table cloth or such can cover it. Another support idea could be stacking cinder blocks behind to stand level with wood if needed to match height ?
6 foot tanks are always hard to move and set up so they sell fairly cheap.Used equipment is usually crappy and quickly replaced..With that said $50 is a steal..You should get it...