The tubular steel exhaust headers were installed up to July 1965 (up to engine number 011153 for manual transmissions or up to engine number 003213 for automatic transmissions) and after that it was replaced with the short cast iron manifolds.
Not a 100% sure about the ZF 5 speed, but I seem to recall that it was introduced as an option in 1965 and was available as such up to 1971. Maybe others can confirm this.