I put new springs in my 68 convertible this past winter. I know darn well that I found all the torque specs in my 1968 Pontiac Service manual (not just a Firebird manual, but a Pontiac manual that also covers full size, tempest, and Fbird.)...if I recall there is a page at the back or front of the rear suspension section that was nothing but a list of torque specs for that portion of the car. Some of the terminology was different than I'm accustomed to, but once I got past the old school terminology I found each and every nut and bolt spec on that page....

On a vacation right now and won't be able to help look them up for a couple weeks, but if you still don't have an answer by then I can do so at that time.

Look again. I know for a fact the specs were there.