Is my rear end strong enough

They're stronger than a 741. At least they have a larger pinion shaft. It doesn't mean they're stronger but they should at least be comparable. Gears matter. The lower the gears, the less stress they are subject to. What tires?? Slicks at the track or street tires on the street? Last is the engine and drive train. A stock engine converter doesn't hit near as hard as a built engine with a higher stall converter.
Sorry if I haven't been any help.

Personally, I think they're plenty strong and will more than hold up. If I'm wrong the worst you have to do is replace it. Which is what you need to do anyways if it's deemed to be too weak.