I would search for "replacement tool cabinet sliding tracks" since they have higher load ratings than those for regular cabinet drawers. A bottom single track attached to your rack frame would be great; but the weight and tank stability is an issue unless you could find one with a large attachment point that remains stable with around a 100 pound load.

Paul's idea might be only solution and could work with either hardwood (1x2 or 2x2s) or a similar piece of angular aluminum providing an attachment point for the horizontal sliders .