OK just found this article
and this from it
Installing the Flex Air Pin Box on our Fifth Wheel Trailer
Lippert’s pin box install manual states “We recommend using the nuts, bolts and washers that came on the coach unless they are in bad condition. Make sure replacement fasteners are the same grade and diameter as those removed for torque specifications on pin box bolts refer to manufacture’s specifications. If no torque requirements exist, torque 1/2” bolts a minimum of 110 ft/lb and torque 5/8” bolts a minimum of 160 ft/lb and torque 3/4” bolts a minimum of 210 ft/lb.”
I reused the OEM 5/8th bolts, nuts, washers as they were all in excellent shape and tightened them up to 160 lbs. I did have to move the new pin box up one alignment hole to have the king pin at the same height as my old one.
thanks to all