If you are going to do anything, lose the 27 spline shafts and get 29 spline shafts. People have different interpretations of what "wheeling hard" is. I have broken two stock 29 spline shafts with 33's, and believe me that the Chryco 8.25 is not an axle you want to have to tear apart on the trail.
It all depends on what type of terrain (deep rock, lots of binding ect...), tire brand/size, locker, and how much you flog on it.
If you must keep the 8.25 and run 33's then seriously consider chromo shafts and a gear job becasue 33's and 3.55:1 gearing blows. I kept my 8.25 despite the failures, built it up, and run 35's. I havent broken a shaft since going to chromolly shafts, but I do rotate the spares in and out to prevent wear and stress over time.
Edit: I forgot that I did twist the splines on this 29 spline chromo shaft with 33's: