Is the steering coupler really necessary?
They only time I had a problem with the stock coupler clearing my header tube is when my car had old sagging motor mounts when I bought it. They must have been some cheap Chinese import junk cause the rubber was squishy and let the engine move around just enough to hit the header. I replaced them with new Schumaker mounts and it raised the engine about 3/8" to where it was supposed to be and it now clears the coupler by about 1/8".