223 Rear Main Bearing Too Thin

Hello

I'm rebuilding my '55 Ford 223. This is my first time working on these.

I just got it back from the machine shop. They included a set of main bearings with it and the part number indicates it should be correct for the engine. However, I find that the rear main bearing in the new set is too thin. It's 1 and 1/8" wide but from my measurements from the block it should be 1 and 5/16". The new one doesn't fit - it's too thin. Am I going nuts or doing something stupid? Anyone seen this?

Thank you

Have you checked your blocks casting / design numbers and date code to verafy its year?