Issue with mounting feet dimensions

So, the info that i have for the elite mounting feet show that the hole pattern is 3-3/16" x 1-5/8".

I machined 4 mounting plates on my mill to these dimensions, but the 4 socket head cap screws won’t all thread in properly. I double checked my dimensions, and I’m spot-on down to 0.001".

If i convert those two dimensions to metric, i get 80.96mm and 41.275mm respectively.

Is the hole pattern actually 80mm x 40mm? And then was converted to SAE and rounded to the nearest fraction?

Why aren’t the holes lining up like they should?

Thanks in advance.