Its believable to me that M-20 could now just be the designation code for a 4sp. I was just told that M-20 stood for muncie and made sense to me because of the M. What does Saginaw mean? Where Its made?yes and no, it is an rpo code, which gm used to specify a particular component based on the car and year. for example, an lt1 eng in 71 is not the same as in 93 or in 2018.
that may be correct for a g body. but his is an A body. in my 79 service manual, the 4speed manual is listed as the m-20 option.
joe
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