I will get you a cut list tomorrow. If I am building it for a customer i like using a prefinished asian birch which is the same wood i build cabinets and custom cages out of. For mine i just use any scrap plywood i have avalible.
Without the bucket each level is 12" apart. If you were gonna use water bottles you could get away with a 5 level that would be 60"
For the cut list I will give measurements for a 4 level rack that way you have the option to use auto water or not.
Most likely I would reduce the spacing between tubs and try to get at least 6 levels in the rack. I do use the auto water, not bottles. I checked again and I could go 68 inches without a problem and possibly a few inches more if I pre hang the bucket.
I used an under tub support system for a "jasbus" rack and fit 7 levels in the 68 inch height and that's with 2 inch wheels. I used 2x2's for that rack with 2x4 legs.