I never tighten any of the suspension bolts until the car is resting in its full weight on the four tires. Also, depending on where I am in the restoration, the Mustang may sit like that for a month or more. Shocks never go in untl the complete drivetrain is installed.
For the record, if there is a specific torque called for by the shop manual for any attaching hardware, I always follow that specification.
I don't think the rear of the car needs a 2 inch drop, rather it may need to settle 1/2 inch to be correct. Kinda of hard to truly appreciate the correct ride height when current radial tires are on the car.
Regards,
Pete Morgan