Why would freeze plugs need replaced?

[crazeetxn]

Back a few months ago, my son's 327 bit the big one...

He's been looking for a replacement and came across a 305 that the guy says he pulled to replace it with a 350. Says it runs good but needs two freeze plugs replaced.

Why in the heck would they need replaced? May be something minor, but I just haven't heard of it when someones trying to sell a block.

He's only asking a couple hundred dollars which is in my son's budget

Thanks for any info!