Here is my 02.
20130613_061834_zps9adfaa0b.mp4 Video by penright | Photobucket
Do you think they sound the same? Was yours like that with the valve covers on?
I am thinking piston slap. I would think a rod would be more hollow, but the last spun rod bearing I messed with was a 454 olds Cutlass and my hearing was a lot better then (younger). But the rhythm of both of ours seem to be fast, like valve train. My first thought was lifter, but now you that you tried lifters on yours. How many miles (sorry if I missed it somewhere)? Mine is 240,000