I have a 70 Chevelle, 350 2bbl, ???automatic. The tranny pan is deffinately square with one corner cut off. Which I have learned this implies THM350. My build sheet says M40 CBC TRANS. According to the build sheet decoding on this site, M40 implies THM400. All this equates to one confused Chevelle owner. Anyone have any ideas? Oh, another thing that points to a THM350 is I got a tranny filter kit for a THM350 and it was exact as the old. Thanks again!!!