8 3/4 question

There are three different carriers.
741 small diameter pinion pre 69,
742 Large diameter pinion pre 69.
and 489 tapered pinion 69 -72.

All three carriers the sure grips and trac-locks are interchangeable. 489's are desired for performance car restoration for 69-72. 741 usually found in trucks and passenger cars pre 69. 742's are found in big block or performance cars pre 69

I use a 742 in my race car with a spool. 741 and 742 came with clutch style trac-locks. 489's all came with the cone style sure grips. I would always replace the sure grip with the trac-lock in my cars with the 489 in my big block cars, less slip with big tires.

I would Just keep the races with the bearings they are on unless replacing the bearings. 741 and 742 are easier to change the gears they use shims on the pinion where as the 489 uses a crush sleeve which should always be replace with a gear change.

I prefer the 742 with slicks at the track. 741 works great with street tires on a street car. although if you get a good 489 set up correctly would be the strongest. I just like the 742 for the convenience of easy repairs.

741's get a bad rap for snapping the pinion threads . But this is usually caused by the housing wrapping up with weak springs on a hard launch which usually rips the yoke off due to the smaller threads holding it on. All the early Max Wedge and Hemis came with 742' if not a Dana car.

The most important add on you can install is a housing brace which prevents housing flex that causes the axle pressure to crack the carrier caps. Hope this info off the top of my head from experience I remembered helps.