IIRC, Workhorse used a couple different rear axles on those...and torque specs might vary by model...
You COULD follow a general torque guide based on the size of the bolt:
https://www.portlandbolt.com/technical/bolt-torque-chart/
OR, if you're not comfortable with that, call Brazel's RV. They're a Workhorse shop and should be able to answer your questions. Be sure to have your VIN handy.
https://www.brazelsrv.com/