For the purpose of better search results on a given subject I wanted to start this thread. There was a recent thread started in another category which is very informational for 65/66 GT350 owners http://www.saacforum.com/index.php?topic=8471.0 . I also wanted to add that there is a identification difference between the assemblyline and the later service replacement valves not previously mentioned. The later service replacement valves are machined flush on the top where the brake lines are attached. The assemblyline and early service units have two small peaks where the machining was done in a circular fashion leaving the marks . Top one in the picture is NOS service replacement. These marks are visible when you look at the valve when installed.