Shells are graded from the factory but this does not take into consideration wear and material lost when polishing the crank.

We have recently rebuilt a 35 gtr engine and that had different sized bearings on top and bottom journals from the factory. For every size of the ACL's available Nissan have 10 sizes.

As mentioned generally the 200sx engines have had a hard time and tuning a engine that is both high mileage and hasn't had regular servicing is only going to end badly. As for this engine builder I think it's safe to say he is doing something wrong.