I would take the block back to the machine shop with the cam and have them fit it. Have them measure the installed cam bearings with a dial bore gauge to see if it the 4th bearing is too small installed or not.
BBC bearings are 3 different outside diameters. They are marked which number on the bearing goes in which bore in the block. I have heard of having to use a knife to clearance a tight bearing before, but have never had to do it.