Just in case you don't know, 35 spline axles for a Dana 60 are the same as 35 spline axles for an 8 3/4, just different lengths, as needed. However, 35 spline is much stronger than 30 spline. I believe Moser may have a comparison of spline counts and strengths on their site. Stepping up to a 35 spline 8 3/4 will make the ring gear the next weak link. Set-up is important.
I broke a Strange 35 spline axle on my 360/W-2 Challenger footbraking @ 2,800 lbs running as fast as 10.22. But that was after about 10 years and thousands of runs. I have Moser 35 spline race axles in my Dart Sport running mid-11's footbraking @ 3,540+ lbs for at least 8 years with no issues.