The 546 plow was adjustable from 14 to 16 inch mouldboards while the 548 was 16-18 in mouldboards. They could be set up either way depending on what size bottom was used and how they were bolted together. The 588 was 18-20 inches and was the highest trash clearence of the 3. By the time time these plows were used the hydraulic reset was all but gone. Some of the earliest models had it as an option. Most were sold with the spring reset, but could also be purchased with a shear pin set up if I remember correctly. If you plan on plowing corn stalks the 588 is the best.