M21 transmition 660 case vs 661

[Mr70]

Yes Peter.
I've personally seen 660's used on early assembled cars,& not just Kansas Leeds built,but all plants,& cars..And Crash just posted this a few weeks ago.

"660 main cases were used as late as Dec. 1969... 661 main cases were used as early as Sept. 1969. I have examples of each... The beginning of the 1970 model year the engineering drawings were change on the Muncie main case so that a fill plug and drain plug were tapped into ALL muncie main cases, so you can tell early 1970 model 660 cases, because they have drain plugs, M-20's, 21's, 22's... Hope this helps...crash"