Dave, when all else fails, you can usually go by a chart according to the size of the bolt and the bolt material. The exception being when threading into something softer like aluminum, or TTY bolts etc.
Here is one you can go by, note that the max torque is 54 ftlbs for a 7/16 bolt like that in grade 5, and that is a dry torque. Any anti seize or oil used would reduce that to roughly 40.
http://www.engineershandbook.com/Tables/torque.htm
Of course if you can first get proper information like that 30ftlbs for the bolt as spec'd by GM, go by that.
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