I'm not sure how they addressed the Cuda exhaust tips. All other models had the exhaust under the valance. Maybe the Cuda tips were installed after the rest of the exhaust was bolted up. I guess it's possible that the rear valance was removed before "body drop". Maybe the Cuda rear valance was painted separately. Cuda's and Challenger's could have had a slightly different assembly procedure.
Basically, the way it worked, is that the bodies were handing from the ceiling on a conveyer. The completely assembled K-member/suspension/engine/trans/drive shaft/exhaust/rear end were on large carts on the ground. The body was then lowered over the assembly and the fasteners were tightened. As you can see by these pictures, the body has been completely assembled (for the most part) before the "body drop" process. The interior is already installed. The undercoating would have already been sprayed too. Notice the front of the torsion bars are hanging from the rear torsion bar mount ready to be installed. My guess is that "body drop" is one of the last things before the vehicle is driven off the line.