Front wheel cylinder problems

Hi Guys, I am working on a 67 barracuda with 10 front drum brakes. Ordered new wheel cylinders and got a set that are different and wont mount. The original ones I took off are a rectangle where they go through the backing plate. The ones they sent me are a oval type shape. I have looked all over the net but cant find ones like mine. Can anyone ID the one I have?? Maybe they are off a different car??
Thanks for any help I can get.