Classic Mustangs have been getting dual exhaust conversions as long as there have been Mustangs. Exhaust shops have carelessly drilled holes and attached hangers using anemic sheetmetal screws. With road shock and vibration, screws pull out, pipes and mufflers drop, and it gets quite embarrassing. When dual exhaust systems were factory installed, Ford used stamped steel reinforcement inserts and brackets that provided excellent support.
The vintage Mustang reproduction market is never short on ideas for making classic Mustangs a better driving experience. The latest are the rear seat area's floor pan reinforcement plates that fit right into any '65-'69 Mustang floor pan. Available from Classic Tube, the reinforcement plates not only provide the obvious, they also locate dual exhaust hanger bolt holes where they belong for easy installation. Although we weld them here, you can also install them using a strong industrial adhesive, which offers a solid bond over a broader surface area if you don't have access to a welder.
You might look at '65-'66 reinforcement plates and wonder why there are differences in part numbers. Both stampings are identical with the exception of rear seat belt anchor points. Seat belts were optional and typically dealer installed for '65. For '66, they were federally mandated in all four places. If you want to install rear seat belts in your '65, opt for the '66 reinforcement plates and install the seat belt anchor nut plates. Suggested retail for the Classic Tube reinforcement plates is $29.99 each plus any taxes and shipping.