How's your oil pressure? Bad mains will leak a lot and reduce pressure, a spun bearing, although I've never actually heard one, is an apparently very obvious noise.
An off-tune sound might be it not running on 8 cyls
I had a turbo Buick that spun a main. It knocked under heavy load, not really any noise if just cruising. I guess the crank was supported by the next bearing except uder load it flex enough to knock. I babied it around for weeks until a rod fed by that main went south too. If it seems like a miss, it aint the bearing. If it souds like a jack hammer inside it is a bearing.