The 340 is out....again.....

I agree RAMM. Hence my comment in post #86.
The cam bearings are not the issue. My feeling is a blockage in the passage(s) between the junction of the cam oil feed and the main oil feed from the lifter galley. I drill those out on all my builds anyway but I've seen some very narrow factory ones in doing that. Especially in later LA blocks. Thing is the oil does not flow around the cam, but to the mains under the cam bearing shell. I can't see potential leakage at the cam killing bearings such as yours. Not with a camshaft of some sort in place and not flopping around in the bearings.