Aftermarket vendors such as Oregon (OEP) have caster parts available, but aren't cheap. I don't doubt you, but am having a difficult time seeing the advantage. Maybe you could explain your scalping issue in more detail. Maybe it is set up issue. If one were going to put casters on this, it may be best to make a bracket up that could be double bolted to the existing deck brackets and hopefully be adjustable.

My JD turns so tight that, while in a tight turn, the deck wheels don't turn but just srape accros the grass causing some damage especially over time and when the lawn is wet. With the swivel caster they turn with the mower. I'm sure the set up is good; the deck wheels are set just slightly above the ground with the deck at mowing height. The casters I installed are bolted to the existing brackets and are far more adjustable than the original deck wheels. It works so well that I am sure some lawn tractor manufacturers must have already thought of it. If you are interested I would be willing to figure out how to post pictures of the casters for you.

Learn at link below.

Here is a link that might be useful: pitcher postin' primer

The deck wheels are not suppose to touch the ground unless there is a high spot.If there set right they will not goudge the ground.

The deck wheels are suposed to be around an 1/8" off the ground but if your yard is not a perfectly flat golf course of a lawn, they will touch the ground occasionally. If your not scalping around certain trees etc. then stick with your stock deck wheels but, I really like the swivelilng castors.

Should be a little more then 1/8'' about the thickness of your index finger should go under the wheel.I have thick fingers.

Sounds like you need to replace your deck wheels. When they get wore down they end up rough and squared off, and tear the grass.
New wheels are smooth and round, and slide over the grass even at right angles.
They get squared off when you turn on pavement with the deck lowered. I always pick my deck up when traversing the driveway or street.

From John Deere's Answer Center:

"7. Be sure to adjust your mower gauge wheels as instructed in your Operator's Manual. They should be adjusted so they are NOT touching the ground when the tractor is parked on a hard surface such as your driveway. The typical clearance is 1/4 inch (ground to bottom of wheel). This adjustment allows the mower deck to follow the contour of the ground without having the gauge wheels actually run on the ground. The gauge wheels prevent scalping of the lawn where the ground is rough or uneven. The result is a smoother look to the lawn after cutting and a longer service life for the gauge wheels."

I appreciate all the great coments. It all comes down to what type of property you are mowing. I have some fairly steep slopes and many small trees to mow around. I reall think JD should consider some type of a caster design for the deck wheels, based on the good results I'm having with my makeshift design. It would add to the cost of the LT so, maybe on the higher end machines.