Sorry to be posting in the 3rd gen, but ppl in 2nd gen arnt talking much and I hate being a newbie ( ok now I found some gears I think would be good but I dont know if they are so I need some more help. They are M20 1963-65 Wide Ratio with 29 teeth,then 22, then 19, and last gear is 17 teeth. I want to stick this in a M21 1974 tranny so I can have a lower 1st. Does this sound good? Is there anything else needed to be done to make this work? Thanks so much!

 

If the one trans is really a 74 and it's really a Muncie and not a Warner, it'll have the 1" countershaft; and if the other gear set is really 63-65, it'll be for the 15/16" countershaft. So, no, they won't work.

But there's no guarantee that any of what you say you have is really what people told you it is; Muncies always were notorious about that. When I was building and trading them regularly I learned early on to never believe what anybody said theirs was until I saw it myself, out of the car.