I was at my machine shop guy's place one afternoon. He'd done a short block for a Chevy 454 customer. When the customer went to install the cam, it went just fine until that last cam bearing. Prior to that, it acted as it should, being easy to turn.
With the engine on the customer's pickup tail gate, Tom removed the rear block plug to expose the rear cam bearing. He took out his pocket knife and shaved the bearing material, all around the bearing, until the cam fit and turned easily. Then put a new plug in the block and it was done. Obviously, it was not the first time for a tight rear cam bearing! So, not just a Chrysler B/RB issue, by observation!
No need to replace all of the cam bearings, just knock out the rear one from the backside, IF there's a plug back there (which I suspect there would be for the initial factory machining.
It's not a "hard fix", but harder the farther along you are in the engine installation process. Nobody's fault that these things happen, either. Just one of those things to check before the engine is installed.
Probably not the first time it's happened at that machine shop, either.
Take care,
CBODY67