I'm in the process of putting a Dana 60 in my 440-6 4-speed RR--will the 30 spline axles hold up behind +/- 500 HP ? Or do I need to bite the bullet and change to 35 spline? Car is mainly street driven but does occasionally hit the track with drag radials.

My stock Dana held up just fine with my 498 6bbl motor. 720 ft/lbs of TQ, but it was an automatic!

What type of 30 spline axles? Anyway I would paint a paint mark on them lengthwise and pull them once in awhile to check them, see if the paint mark is still straight and pay attention to the splines to make sure they aren't twisting. I'm assuming you're using 8 3/4 axles but that doesn't make sense because the Dana axles have to be a different length side to side.

Sheldon