I ran a 741 case 3.91:1 in the 12-second charger for years till the limited-slip started making noise, so even the "weakest" 8-3/4 is still pretty good in my book. 742's seem to be harder to find. The 489 with a crush sleeve eliminator kit might be strongest?
There are two different U-Joint yoke sizes, but also two different pinion spline counts making 4 different possible yokes. I think the 10-spline large U-joint yokes are really expensive compared to the other three, but I haven't looked into it in years. I went with a Strange S60 with spool when the Limited slip started making bad noises.