do you guys think i should replace the outer drive in my rear diff? or do you think i can grind out some of the radius and be good for a while?

Replace.

Definitely replace.

I'd replace, only $10 for 2. Well worth buying 2 sets at that price.

I guess i will. Ill just pick up one set because the others are all fine. I don't want to sink any money into the st1 because i know i will replace it with a kit next year maybe.

Just swap the left outdrive over to the right and the right one to
the left.

surely its the slack thats a problem, not the curved groove it has worn? slack would cause more of a jolt to the drivetrain during sharp acceleration, which would cause more stress on the engine and drivetrain than the smoother acceleration you get from a tight fitting cup

ill have to check my rear bearing to see if its causing extra stress. other than that i dont know what would cause it to wear like that. slack makes sense but the would involve me pinching the cup to reduce it.