C7ME-A BLOCK CAST NUMBER, NOT A 428 ???

Alright, I just bought this short block assembly with 427 heads (C8ME-A), and when I took this to local engine shop, they measured the bore and told me this engine was NOT 428 due to the 4.05 cylinder bore and they thought the crank was incorrect because it was not a steel crank !!! The Engine Casting number is C7ME-A ........ should be a 428 according to my research and in books that I bought for reference. Is it possible, that this might have been a SERVICE BLOCK that was bored for 4.05" instead of 4.13" ??? How would a C7ME-A block have a 4.05 inch bore ??? I really need some help on this one, if anyone out there KNOWS for sure what we have here !!! I am located in Memphis,Tennessee area. Send me an e-mail, if possible ........... markcasillas1955@yahoo.com