273 HiPo air cleaner base inside diameter?

Ok, tired of searching, thought I would ask.
What is the i.d of an original base plate for this air cleaner.
I bought an air cleaner assembly that is supposed to be original.
The base plate I.D is 4 1/4"
The Carter afb on my car is not original and measures 5 1/8" across.
Help me out please.