WJ knuckle swap?

I know there are alot of threads on this subject. I have searched and read them.

I have a 1998 XJ w/ the stock D30 front. The WJ knuckles are front a 2004. I have everything from the knuckle out.

I have some unit bearings from a 98 ZJ. I measured from the hub mounting surface to the rotor mounting surface on both the WJ and ZJ unit bearings and they are the same. I used a digital caliper.

I have read that I need a .25 inch spacer between the knuckle and bearing to recenter the axle u-joint between the ball joints and center the rotor in the caliper.

If they mearsure the same do I still need a spacer between the knuckle and bearing or can I just make a smaller spacer to go behind the washer and nut for the axle shaft to recenter it?

Thank you for all your help.

Yes, you need the spacer.

No, the ZJ hubs won't work, you need 2000+ XJ/TJ hubs with WJ rotors redrilled 5x5.5.

The idea is to center a WJ rotor on an XJ knuckle/caliper, comparing the hub to a XJ or WJ depth won't really tell you much.

I redrilled the rotors to 5x4.5. I'm also reuseing the WJ calipers.

I'm sorry I don't understand the importance of centering the WJ rotor on an XJ knuckle/caliper if I'm useing all WJ parts except for the unit bearing. i would love to understand this importance.

Thanks again