I raced my stang a lot for at least 2 race seasons pulling 1.9 and 2.0 60ft times. The car sat for 2 years, and not much longer after it was running again, with a slightly different setup (lower control arms and slicks), the axle snapped. Once it was fixxed it pulled a 1.7 60 ft. Now I can't say if it was because the axle had a lot of abuse on it already, or if the new setup was the cause, but I think 1.7's is pretty hard on the stock axles.
Spent the last 3-4 years anywhere from 1.69 to 1.85 60's. Launching on either ET Street or Slicks anywhere from 4000-6250 (rev limiter). There are a lot of variables, but I can say mine most likely hold up due to the tires spinning on every launch. Dead hooking would probably kill them, but a little tire spin and they seem to hook well enough and not break anything!
When I had stock axles, they survived many 1.6 60' on et streets with the 331, plus many more before that with the stock motor. They are pretty strong.