I too have serious rust on that same area. I just replaced all the front end components and had to cut out metal on the support area just to get the old nuts and bolts off for the guide rod bearing bracket. The tower area is badly rusted and I was concerned that the integrity of the entire front end is now compromised. Since I am not set up for welding in my garage I put the front end back together and sprayed "Great Stuff" type foam into all the frame rails and open rusted tower areas. That was 2 months ago and my front end feels as strong as it ever did. I'm not sure what is holding it all together but it all works fine.

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Orland Park, IL
1985 300SD 215,000 miles