He has a 1970 T/A, so all of them had the 'new' setup that entered use on Jan 1, 1970.

There is a two page TSB about it and how it functions at https://www.hamtramck-historical.com/images/TSBs/1970/D70-5-1%20page1.jpg and https://www.hamtramck-historical.com/images/TSBs/1970/D70-5-1%20page2.jpg