the only reasons not to do a 6.0L swap is if you are concerned about fuel economy, if you can put something larger in, or if you race in a class that has a displacement limit...

 

6.0 no doubt

 

i cnat believe no one said lifters. dude the sound you are hearing could be your lifters. the noise stops because they are hydraulic and have to pump up. try going to a heavier oil and see if that helps.

 

Yeah, I've tread everything. 20w50 oil with some stabilizer, still sounds just as bad. Don't really know what else it could be. The Piston slap sounds about right. It's more like a knock than a rattle. Thanks guys for all your input.