Was just going to post the Off Road set, picked one up about a month ago. Looks like it's part of the old Desert Rat kit that came with the Datsun and one bike.
For most of the parts needed I would start with a Monogram Tbird pro stock kit and the red Monogram Cobra kit sine they are the same scale. Would probably need to adjust the wheelbase to fit the Mustang body. Good luck .........