The old Detroit's are all two cycle.
GM diesel division started with the purchase of Winton engines, really big two cycle engines. They then quickly developed the 71 series and sold them starting in about 1938. The last two cycles sold to civilians was in 2000. The military still bought them for a few years after that, and perhaps still today, but I have a feeling not any more.
I don't know the date for the 8.2 (four cycle), but about 1980. The 60 series came out mid 80's I am guessing. Some of the other newer 4 cycles, like 40 series are IH based, same as the DT466, but with Detroit electronics. Please don't be afraid to correct me, as I know very little about the 4 cycles.
