What is the torque spec and tightening sequence for a small block Chevy 350 aluminum intake manifold?

Start in the center and work your way around in a circular pattern. Torque in 3 stages with the first stage just to feel them touch, then to about 20 ft./lbs, then to about 40 ft./lbs on the final step. Almost any repair manual would have the exact pattern recommended by the manufacturer.