Fastening torque specifications - Tensil load

I'm working on setting up torque specs for a manufacturing line installing stainless steel screws attaching a flat piece of aluminum into another but perpendicular aluminum boss. The face of the attaching piece is 0.080 inch. The opening is slightly larger than the screw. The screw is a 1 inch # 8 16 preped with screw grease going through the face of one piece and into a split boss which is also has 0.080 walls. I have reviewed the screw manufactures torque maximum specs which is good for the max capability of the screw. The question is focused on the actual torque of the attachments of the 2 pieces. The question is - how to determine the torque for fastening the 2 pieces using the dissimilar metals given the dimensions of the material and fastener.