GT54 deck issue
 

This is on the 1863, I've checked all to online resources I can find, as well as looked for damage or mismatched parts.

The rear deck wheel on the non chute side rubs against the deck, I currently have a well worn one on there which doesn't rub, but a good one will.
My thoughts are that that corner is supposed to have a different axle or a spacer, but I don't see anything like that on partstree.

Here is the parts breakdown for the 190-324-100 (GT54) deck.

190-324-100

Rear deck wheels and casters are the same. You don't have the wheel turned to the inside do you? This is how it should be setup.

That shows both0 sides as the same part. This may be case of looking but not seeing on my part, I think those wheels can be mounted backwards changing the offset...

That's how it's set up; the crown of a newer wheel just touches the flange around the deck, the one I have on there now is worn flat and clears. I may have a small bend or twist in a part or the wheel backwards, luckily I have spares of everything.

I had a better look at my deck yesterday, it will only go one way and it is a very close fit, maybe 1/4" clearance at best. They are also easy to bend the axle / shoulder bolt so that may be your problem. Post a pic of yours.

Grease fittings go to the outside. If they are to the inside, that'll move the wheels I/B.

I looked at one of my 54" decks. It's a little worn on the spindle and deck mounting holes so the spindle will rotate some. Wheel and bushings are worn a little. If I backed up, the left side wheel would rub the deck.

Don't see it as a problem unless your wheel is hard against the deck.

Here's how it looks with old wheel on. It doesn't "look" like anything is bent, but the PO had to have hit something pretty hard at one time because I had to spend some shop press time straightening the deck hanger assembly.

This is a 54" deck that I had a few years back. Obviously the wheels are very close but I don't ever recall them rubbing.

If you lower the wheels they will not hit.