1 One of the best upgrades you can probably make to your ’65-’68 Mustang is a set of high-back seats with locking seat backs. The early seats not only do not lock, but the low back height in an accident can cause serious neck, spine, and back injuries. A popular upgrade is a set of Fox Mustang GT seats (’82-’93), as they bolt right in with minor seat track mods. The ’94-’04 Mustang seats will work as well. We found this pair of seats at a swap meet.