I believe that I tightened mine to the 45 ft.pd. spec. That U bolt is probably not a grade 5 or grade 8 bolt.
It would be correct to do the final tighten with the weight on the suspension.
C
I'd bet they are grade 5. But a 1/2 SAE bolt for grade 2 even shows 55 ft lbs. A grade 5 shows 85 ft lbs but that is dry. Lubricated grade 5 is only 65
Still another torque chart shows grade 2 dry / lubed at 55 / 40, and grade 5 at 90 / 65 ft lbs