I was thinking of picking up a ZZ4 shortblock, and tossing some AFR heads on it.

Now, the crate version of the ZZ4 shows redline to be 5500 or so. Is this because of the lower powerband of the crate? Or is that the maximum the engine should be revved up to?

Does it matter more on what heads I have, then it does what the shortblock is for maximum rpms?