[jester911]

I use a Das bar that attaches to the seat belt points. It isn't the most ideal (welded in would be)
but it is PCA DE legal, it stiffens the car and the harnesses attach very nicely to it making it very good on the track.

You may want to consider doing something similar if you do enough track days to warrant it.
Another possibility is to have a harness bar welded into the bar you have. Just a thought.