eh...sorry. 742 is considered the strongest. The 489 pinion has a SLIGHTLY larger OD, but that tapers down to a narrower section, than the 742 diameter. Therefore....the 742 is stronger. It is also easier to set up without the taper.
I believe the 440 six-pack and Hemi cars in the late 60s all had factory 742s, until 489s came in....(69???)
