I have a friend w/ a 2004 5.7 hemi that dropped a valve seat and chewed a cylinder.
He's looking to get a replacement motor, but doesn't want to run into this issue again. I know the early hemis are known to drop seats, but apparently they fixed this issue in the 2009 models?

What is involved in using the '09-up heads on the earlier motor? I've been told I'd need to get the valve covers and coil packs for the newer heads. Any other differences?
How much does the compression increase doing this swap?

Would it be easier (or even possible) to use the complete 2009-up motor in the older vehicle?