All of the Energy Suspension body kits I have purchased came with an instruction sheet. Here is an example of what appears inside the box that I obtained when I ordered them new from Summit.
This sheet is the first one to pop up on a Google search. If you have a part number you may find your missing sheet.
In this instruction sheet it states to tighten the bolt to the factory specification which is written in the Assembly manual. I don't know what year car you have Mike but I am sure If you look in your Assembly manual you will find that value as every torque spec of every fastener is called out.
Which is unusual considering the line workers don't have a torque wrench, all of the pneumatic impact guns on the line are pre set with the correct torque and every station assembles a different part with a different gun set just for that one part.
If you have a 1964 Impala then you could find an assembly manual here if you didn't have one (that is two ifs reducing the possible number of yes responses). You could buy one here if you needed it for $20 bucks.
While trying to find a toprque value for any of the bushing bolts and assuming you have a 1964 since it is one of the most populat years I found replacement bolts just no torque value yet.
See I'm still looking:
The closest info I found so far is "1967 Buick Chassis Service Manual Section 2" go to "Section C page 20-16" I found mounting specs and diagram for an X-frame Buick; just not for a Chevy though probably exactly the same: the torque specs are 30-45 ft/lbs which isn't a value, it is a range, which makes think I need to look further.