How are grade-level garage slabs typically connected to a basement wall?
Be careful. You are about to change the "structural dynamics" of the basement wall. 

When concrete walls are poured, reinforcing steel is placed on the TENSION side of the wall. In your case, the concrete wall is designed as a retaining wall. That is to say, the concrete wall is NOT restrained at the top. Therefore, the reinforcing steel is placed in the outer one-third of the wall, (soil-side of the wall).   (By the way, the floor joists sitting on the wall, parallel or perpendicular, do not count as restraint the top of the wall. The wood will shrink over time and the wall will be a retaining wall.)

If you restrain (connect) the top of the wall to the garage slab, you've changed the wall from a retaining wall to a beam. Now the tension side (and reinforcing steel) is on the inner (room-side) one-third of the wall.

If you connect the garage slab to the top of the wall, you'll have failure (cracks and possibly crumbling) depending on how "wet" your soil is...

Go see an architect or a STRUCTURAL engineer, not a CIVIL engineer.