Biscuit mounts thick vs. thin

I was going through the parts pile I have and noticed that I have two different biscuit mounts. The thick one has a part # 2265 on it, and the thin one has # 2266.



The thin ones came out of my car with the Schumaker mounts attached, the thick ones came with a set of 340/360 brackets that I bought off a member here. Both numbers are listed as fitting a 67-72 A body on RockAuto.com

My questions are, what are differences (other than the obvious), which mounts came with what engines, and what mount should I run on my 408? Thanks in advance for any help you can give!