I don't see a page 4-29. Torque specs on page 4-19 do not include the rear axle U bolt nuts. Best I found elsewhere was generic for the U bolt shank/thread for grade 5 and 8, not specific to Firebird. This pdf contains some good info on the importance of having these installed correctly (especially why to never reuse U bolts, the difference between dry and lubricated threads, and also to re-torque at 500 and again after 1000 miles). My springs are ok but my axle slipped forward an inch on the driver side because these were not tight enough - ride and drive-ability were adversely affected to say the least...
