bringing this back from the dead. But I would not use Insane. seen my buddy go through 3 sets of the 500hp shafts and he is well below 500hp. the metal is junk. even with preloading they still broke. and the shaft looked like an ice cream swirl. I'd go with DSS or at the very least OEM not rebuilt.
I've been using my stock ITR axles with my K24. Engine has ASP big tube header, 12.5:1 compression Supertech pistons, RBC manifold, and 74mm throttle body. Used to have a K20Z3 head with Brian Crower stage 3 cams. Now the engine has a K20A2 head with K20Z1 cams. I have had no issues with the axles even with doing gymkhana/ autocross events monthly.