I remember reading that some bell housings were as much as 0.040 out from the factory and in one factory manual I recall a method for correcting it with offset dowels. That seems preferable than shims to me. That said, I've never even checked mine and that bell housing has been on two different engines and I've had no clutch-bearing or pilot bearing problems in 50 years. And that's just my present truck not to even remember all the other ones I've worked on. I've never had a bell housing misalignment cause a problem. If you're within 0.010, which you are, you're well within the manufacturing tolerances of the day.
