1969 thermostat housing

[john302]

When did the 660 casting number move from the outer lip to the neck of the housing? Always thought the top neck location started in late 69 . Seen a few january of 69 cars with the 660 number on the neck . Thoughts?

[rszmjt]

My 06A RSZ has the original thermostat housing and the “660” is by the outer lip. I’ve owned the car since 1974 BTW.
Additionally I have a survivor 1970 Z28 CTB Motor with 6,000 miles and it is by the outer lip also. It has never been off.
I have noticed that cast intake cars had it on the neck, and pretty much all the original aluminum intake cars had it by the outer lip. JMO.

Hope this helps.

Mike