The system is designed to be used in conjunction with a set of long tube headers. Convertibles will require some modification for fitment. A system using 2 ½ inch pipe for a 1965-’66 Mustang is part number 12134 with a price of $474.95. A three inch system for the same car would be part number 12132 and list for $624.95. For 1967-’70 Mustangs the prices are the same. For more information contact Mustangs Plus at (800) 999-4289 www.mustangsplus.com