What he was getting at is the vette is closer to 50/50 weight distribution so while the mustang weights more the weight on the rear might be very close.
Vette = 50/50 (3200x.50) = 1600 over the rear "axle"
Mustang = 54/46 (3700x.46) = 1700 over the rear axle.
So the mustang only has 100 extra pounds in the rear. I know the distributions are correct, not sure about the weight as I just used what you supplied.