Looked at images on Google and they certainly look the same except the Buick version has "Buick" cast into it.
Thanks Rocky, I think the same and the extensions a slightly different and the Buick casting but I think they have the same geometry, being in Aus I cant just get two cars lined up to check.
I typed in "52 Olds grill" and images of 52 olds and buick grills popped up. Some of them with both makes next to each other.
Be sure what you purchase fits as I believe Buick had 2 sizes. I cannot remember for sure if the Specials and Supers are the same (I think they are) but the Roadmaster is larger width and length wise. I am guessing IF the Olds and Buick interchange that Olds probably had the same size difference depending on the model it came off of eg. Olds 88 or 98. I am just guessing though. I remember while I was searching for the upper mustache for my 51 Special running into this. I came across a guy selling a rechromed grille for a 51. He too thought it was the right one for his car and had it all redone just to find out it was the wrong width and that was why he was selling it on ebay. Get an interchange manual. Come to think of it I should get an interchange manual.