I'll be blunt, but you may need an engine.
The cam bearing will 'walk' out of it's seat, and cause oil pressure to drop, you'll lose pressure to the rear lifters. I can't explain this next part, but I've seen several people send the block out to have a machine shop go through it, new bearings and all, but the noise will persist. I do not know if there is, and have not been able to find on inspection, anything 'wrong' with the block when this happens, but a short block is the only effective repair I've personally ever seen when this happens.
I am not condemning your engine, as I have not heard the noise, and it could be something else, but if it is the cam bearing issue, don't waste money trying to fix your engine.
Also, and don't take this as me saying everything is ok, but I have seen people drive for years with this noise, with no real adverse side effects.