There isn't any junction box that can bear the weight of most track lighting. The track is supposed to be attached the the ceiling elsewhere. Are you saying the box sticks out too much for the track to sit properly?

Yes, the box sticks out beyond the ceiling drywall. The former light fixture disguised this problem. I might have the wrong term, it is the box to which an overhead fixture was wired. I removed the fixture to replace it, and discovered this.

I would like to add track lighting that sits flush with the ceiling, but the protruding box prevents this.

How is the existing box attached to the ceiling? I don't know how handy you are, but the options would be to reset this box so it's flush, or to replace it with a less deep box that will be flush. Whether you can go with the latter approach (smaller box) will depend on whether you can satisfy the box fill requirements of the electrical code with a box of less volume given the number of wires you have in the present box and what their gauges are.

If the track lighting has a hole large enough for a cable clamp you may be able to eliminate the box completely.

To clarify, the track will eventually also attach to the ceiling with molly bolts.

I will take a look at the box and try and determine how it is currently attached, I'm not sure. I need to wait until my DH is home as I don't want to tackle this without backup.

Brickeyee, what is the cable clamp to which you refer?

Thanks, everyone for your help. I learn so much from GW!

The cables used for permanent wiring use clamps were they attach to a box.
Some fixtures are also designed to have a clamp installed so that a cable can enter directly.

The hole would be around 3/4 inch, usually at one end of the fixture.

The problem with smaller boxes is box fill.
The NEC requires a certain amount of volume based on the number of wires, devices, and internal box clamps inside the box.

The thinnest box for general work is about 1.25 inches deep and 4 inches square.
You can install a plaster ring (making the overall depth 1/75 inches).
If the box is in a joist cavity there are mounting methods that can recess it deeper unless something structural is in the way.

This sounds like a single story house so why not
go into the attic and reset the box flush with the ceiling?
If it's not accessible from the attic use a fan box to straddle
the stud. It should provide enough CU. In. for the box fill.

"If it's not accessible from the attic use a fan box to straddle
the stud. It should provide enough CU. In. for the box fill."

The "fan boxes" often rely on the canopy volume to meet box fill.

Track lighting does not normally have a canopy.

Failing that the link below is 24 cu.in.

Here is a link that might be useful: SBFAN New/Remode Box

"Failing that the link below is 24 cu.in."

And VERY deep.

The fan boxes that come with an expanding screw brace and fit through the box hole are very nice for rework and are nice and solid with locking hardware to mount the box to the brace (nylon locking nuts).