Wow that explains why only passenger side was rotten!Not only that but it gets clogged with rust and debris as well. I wire brushed mine, used etching primer and good automotive paint to help keep them from deteriorating. Also, the AC condensate drain discharges over top of the passenger side mount providing a constant supply of water.
Like you said…..GM didn’t think that one through very well
Anyways, here’s the results.
Took me hours to get bolt out, it was melted inside.
Welded until it break apart, then drilled and tapped for hours.
Once it was out, cleaned area and temporarily welded sheet metal piece where it was rotten out and painted with rust remover.