GM replaced the u-bolts that connect the lower a-arms to the cross member with much larger units. The bolts on my truck were 7/16" and the new ones are 9/16". I figured GM increased the size of these for a reason and I'm guessing these have never been replaced since my truck was built 44 years ago. So better safe than sorry. The old u-bolts look pretty wimpy next to the new bolts.
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I had to enlarge the holes to accommodate the larger u-bolts.
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Here is the first one in place. Only three more to go