Z9s are fine on 3.5s as long as they don't have a oil cooler sandwich at the base of the filter like a 3.9.
BTW my piece of semi useless info for the day.
DID YOU KNOW that the gasket for the cooler sandwich is the same as that found on the filter (logical when you think about it) and a good use for an old filter gasket is to renew the sandwich gasket to prevent leaks, as the filter generally only does say 5-10 K while the sandwich gasket has been there since Abdullah put it there on the production line 20 years ago.
Regards Philip A

