If I'm doing a low deck engine I order main bearings a few weeks in advance from Hughes Engines. Hughes will chamfer them and get them coated but it takes time.

Hughes can't make what doesn't exist though so there aren't any 3/4 groove bearings for low decks and there probably aren't any 0.001 undersize bearings so your crank grinding has to be spot on.

If you are dealing with a shop that doesn't do a lot of Mopar engine they might not know this stuff. If they do a lot of Chevy engines then they are used to being able to order coated bearings overnight delivery from Summit.