Happy,
I replaced the wheel in my 87 wagon following the help offered by this site. When it came to the 10 mm hex bolt, someone had mentioned using an impact driver, the kind that you strike with a sledge. This tool puts far more torque on the bolt than an air impact wrench does. I too had no luck with a breaker bar. Three or four hard taps and the bolt was ready. It was still hard to remove it, but it came out. Should you try this method, use a very good quality hex wrench and also don't use the steer-lock to hold the wheel in place. Get someone to hold the wheel after you turn the key to position 1; you will not have to replace the steer-lock if you follow this procedure. Also, disconnect the battery first.