Here is what most around here call a landplane.
A 100 miles north of here they call them a float.
They are 24 ft wide. Always used after deep breaking and around fields in the early fall before planting wheat on the turn rows.
Here a link to an out fit that did build them. Don't know if they still do or not.
http://www.loepkymfg.com/page/page/1666573.htm