[SFfiredog]

Most modern piston manufacturers utilize aluminum alloys and piston skirt designs that require .0008" to .001" cylinder wall clearance per inch of bore. For example, a 4" bore 351 would have a cylinder wall clearance of.0038" to .004". This is much better than the older style pistons that required .006" to .008" clearance. Those would slap pretty good on a cold morning.
Rod length and deck height also have a lot to do with how noisey a cold engine is as well. I too agree with Fixit. I put forged pistons in just about everything.
--Mike