why do you need a cross over???and yes I know about what they add to a system and there are several ways to do it, some more helpful than others.
If it is a NJ state requirement, a good place to do one for compliance could be under the differential since it doesn't move and wouldn't need a lot of clearance.
You also could maybe just cross the pipes from 2 cylinders under the
oil pan area and run the others straight back ( or even into side pipes((with cats))