Mopar Performance solid flat tappets are listed as .0005” undersize.
I have a set from a couple years ago, and some from 20-25 years ago.
They measure .9030-.9032.

I wonder how many countless thousands of motors were built with MP solid lifter cam kits, along with the .903” lifters....... that didn’t have any oil pressure problems.
I know I used many sets of those lifters through the years....... never an issue.

If you look in the Hy Lift Johnson catalog you’ll see that the early Chrysler solids are listed as being .9035-.9040, so the MP lifters are .0005 under the min.

The newer “universal” Chrysler/AMC pushrod oiling hyd lifter is listed as being .9040-.9044.