http://www.chuckschevytruckpages.com...que_specs.html
Ya that does "seem" rather high but thats what the chassis torque specs show.
1/2" grade 8 fasteners
torque at 90 foot pounds and 5/8" grade 8 are
159/180 ft lbs. So I guess they're using the 5/8 size fasteners?
Maybe someone in engineering can assist.