Fastest Duster on stockish suspension?

IMO, if the car is light and not subject to a heavy shock launch load, it’ll be OK. Personally I would not want to push a 8-3/4 past a 550 lbs/TQ level and be pounded on with a 4spd side step of the clutch type of life. At least with an automatic, you can load the transmission at the line, foot brake or trans brake and release the beast.

Do you have high strength axles in it?
As I said earlier, I wouldn’t go to far modifying the stock rear axle. Just the axles w/green bearings, a back brace and reenforce the axle perch’s. Guys have gotten the high strength caps for the center section and gone through other mods, for myself, it just becomes a lot for something you could have upgraded to a level that has no worries. Then the choice is a DANA or a Ford 9.