the trail guide wheel is very important in making a disc plow work, or pull straight.
the disc blades push the plow to the left, the trail guide wheel must be angled enough to push back and keep the plow running straight.
most old disc plows were put in the fence row when the rear trail wheel disc blade (straight blade like a plow coulter blade worn down and could no longer bite in enough to keep the plow running straight.
my friend and I have two ferguson disc plows, picture attached is the other disc plow, both work great: I had to replace the rear trail guide blade on both of them first thing.
I bought a flat plow coulter blade 18" I think, laid the old blade over the new one and used my torch, blew the mount holes into the new blade,
worked like a charm.
again: you must be able to adjust the rear guide wheel and it must have enough bite to it, to keep the plow going straight.
otherwise, a disc plow will not work.
on the plow disc blades themselves, you can take your 4 1/2" disc grinder and sharpen the edges of the main plow blades, if necessary.