I have a Compact Ford 1700 4x4 needing new rear tires. It came with 4 ply AG tires. I had them filled with fluid and the rims are badly rusted. Need suggestions about ply ratings for replacement. Should I buy 4 ply again or 6 or 8 ply as replacements? My main use is for snow clearing, driveway grading, mowing and rototilling. All for my home use only, not commercial. I plan on replacing the rims and leaving the fluid out. Any Suggestions?