If you have balance shafts, check the chain adjustment. When loose, it will sound just like a rod knock.

As you already know, a good gauge is helpfull.

Cut the filter and look for bearing material or send a sample to Blackstone for testing.

87 Turbo Intercooled Raider, roller cam, torsen rear diff, LSD front diff, lockup auto with modified converter, V6 brakes, low transfer case gears...