Rocker arm measurements

RRR, Why don't you want to use the stock rockers? What you are trying to do seems like a lot of effort for little to no gain. If you were using a readily available rocker, and trying to get a higher ratio (IE 1.6) I could see more sense to it. Stock slant six rockers are getting harder to find (new), but I think the buicks would be even harder to find.
PS: I think at one time RAS did have 1.6 rockers for the slant.