JD used these tail wheels to hold the rear of the plow up vertically and laterally to balance moldboard / furrow slice pressures. If you would intend on using one without a tail wheel keeping the plow pulling straight might be a real challenge. Later models of JD and other make plows that did not have a tail wheel utilized an extra long landside to alleviate the furrow slice 'pulling crooked' problem. You should be able to procrure a tail wheel from any newer style JD integral plow such as F110/ F120/ F115/ F125 that would bolt up to your plow just fine. One side note, JD used a 4.00x8 solid rubber wheel on the early 810 series plows whereas the later used either a 21" diameter stamped steeel wheel like the other guy posted or a 4.00x12" pneumatic rubber tire.
Tyler in IL