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I would be hesitant to heat those U-bolts as you do not know the steel type or heat treat they were subjected to.Heating and reforging them flat could affect the strength.
Why take that chance?
I agree with that.
It seemed like the best idea at the time when I did it now 11 or 12 ago, and has given no trouble. Still I'd look for other solutions as given above before having u-bolts forged again.