The V8V Coupe, V8V Roadster, V8V S, and V12V are all the same width, 79.5" front and 73.4" in the rear..the body panels (skins) are all the same, there is no change...not hating on you ..but this dealership you mention should finish there online training courses that informs them of this..Only exterior change from V8V to V12V is the bumpers/hood/skirts.. Under the V12V uses the undtrays found on the V8V roadster for "stiffening" not for higher speeds, otherwise the Roadster V8V would have no more use for them than the V8V coupe. The trans in the V12V if I remember right is the same just the ratio's are different so it's a different part, just the torque tube+shaft have been revised along with the trans mounts..along with the exhaust center section..The "front" big change is the V12..to fit the intake manifold had to be redone and shorted to fit the width of the vantage chassis, along with the exhaust. The front subframe is completely redone(well just wider and mouting spots for the V12V to fit the V12..the oil filter house has been revised and the location is slightly different that the usual V12 spot..Second PCM for secondary bank was fitted to the LHF fender area to simulate the same spot on the RHF for the primary bank PCM (usual spot for the V8V single PCM)