Whats the difference between a shroud for a non ac car and one with? Can you use the shroud for an ac car on a non ac car?

Difference in shrouds is between small block and big block, big block shroud cannot be used on small block engine, and vise versa.

i've seen it as this,small block non a/c 21" radiator,a/c 23" radiator.big block all by its self.

Thanks guys. found out the non a/c shroud is 2" shorter.