Were the HG's actually leaking? Usually the LIM gaskets let go. Anyways, sounds like it was eating coolant and took some bearings with it. If you're getting a flickering oil light at idle, I'd get a true mech or electric oil pressure gauge on there asap and see what the actual pressure is. That will tell the story. Oh, and be sure the oil is actually full.
Worst case take a video of it if you can so we can try and hear this "rattle". You can also youtube search for 3800 rod knock and see if the rattle sounds like those.
