I have that set too. I thought "V" indicated the mount went into the seat area. It's not a very good picture. I guess it really indicates the car's frame.
This car has been apart a while and happens to have two vertical holes in the seat area precisely where the dual exhaust has its holes.
When I think this through now, the single exhaust has its mounts hung from the frame, but the dual exhaust has it hung from the seat area requiring the additional support. I wondered why a single exhaust would use the seat area on one side but require the use of the reinforcements when using dual exhaust.
Before this car all my Mustangs were factory dual exhaust cars of other years so single exhaust is a foreign concept.