Blazin' Bob, I need to remind you that 741 production carried over into the '70s and they came with the cone type Suregrip.

I also need to remind you that it has been 40+ years since the last 8 3/4 rolled off the production line. In that time any differential may have been tinkered with. For a while it was easier to get an Auburn cone type than the Powr Lock. You never know until you open it up.

Also, you make it sound like every 741 or 742 rear had a Suregrip factory stock. I'm sure you know that this isn't true, far from it.

You are more likely to find a Suregrip under a pickup or station wagon that someone used for towing, and in the high performance cars.

To the OP: The rear end only has to stand what the tires can resist. 741s outnumber 742s and 489s by probably 5:1. I have used a 741 in my '64Dog D100 and have made several long pulls with 6000 lb of trailer behind me. I have had no problems except for seals getting old.

IMHO the best and smartest thing you could do is telephone DoctorDiff. If you buy a limited slip, get it from him as well.

R.