Cases are linebored and mesured in probably tenths of a thou, then marked as to size.
If there is even 1/2 thou shift in centreline, between 1 case set and another, it may never fit, ie bearing to tight, or too loose with proper shells.
Might be interesting to check it out if both case sets were stamped identical on the bearing sizes, but they could easily be all to tight, too loose, or maybe even both?
I am sure someone has done it and gotten it to run (by mixing shells), but gonna be a nightmare for future bearing replace ment.
BTW my 69 cases are stamped with batch numbers at rear, around corner from countershaft sprocket.. if this continued on later models, it would def be something to check when buying an engine.
