I have a M410 that came out of an 1800E in my 122. There a plate on the bottom that's clearly stamped M410. It bolted right up to my M40 bellhousing. I also have an M410 from a '74 164 that I bought for my 164 auto. The two boxes look different in that the 164 box has a different mount, the input shaft is bigger, and the tranny bolts up from inside the bellhousing instead of outside. Therfore I think that there was a M410 for both B20 and B30 but they are quite different. I'm told that the M400-410 was made by ZF in Germany. My experience is that it's not as smooth or easy to shift as the M40-41. They say the M400-410 is stronger but I don't know.