Re: 3.0 noise issues
I know the 4 liters alot better, but as far as piston slap is concerned, I don't think its a big deal. I remember seeing something from Ford that the pushrod 4.0s sometimes had it at startup, and it went away after a few minutes. It said it wouldn't harm the engine in the long run, and is just noisy. Its probably the same for your engine.
pinging is usually from carbon build up, maybe you can try doing a seafoam cleaning or something along those lines. hopefully some vulcan-knowledgeable people will chime in here too.
2002 Ranger FX4
4.0L SOHC, 5R55E Auto, 4.10 8.8 Torsen, 31x10.5/15 BFG ATs