I have a 90 Si hatch, the front passenger side knuckle only has 3 lugs. Rather than take the knuckle bearing out etc I'd rather just replace the whole assembly. Would a DX knuckle work? Couldn't I just swap over my Si rotor and caliper?

DXs and LXs are as common as dirt in the junkyard, but Si's are extremely rare.

 

Si, DX, LX - they are all the same 88-91

 

yup. those three are the same thing.

edit: this slow connection owns me.