Six egg yolks would be the direct replacement for 3 whole eggs. However, this recipe seems to be relatively low on flour so I would keep at least 1-2 whole eggs in there for the structure.
I agree, the oil, since it's such a small amount, seems unnecessary. I think you could also easily replace the milk with half and half. As a matter of fact, if you read the whole thread I posted, I think on the first page of that thread Betty talks about how she replaced the milk with coffee creamer one day because she didn't have milk.
I am going to make the recipe the first time as listed, which is what I always do. It will be my "control" recipe. Then I might start modifying it if I think it needs to be improved. I did read the whole 9 page thread, and the crumb seems very loose which is why I was asking about the cake flour. Generally cake recipes which use AP flour have a more open, coarse crumb.
What I find interesting, is that some people say it is light and fluffy like a cake mix, and other people say it's dense and close to a pound cake. I like a denser cake with a finer crumb, which is how I came across this recipe in the first place. I think I Googled "dense yellow cake recipe." I am going to give it a whirl this week. I am excited!
