I did the Wheeljack leg mod last night using a Reveal The Shield Turbo Tracks that I found on clearance. There are a few different ways you can do this mod that involve Dremmeling the Wheeljack parts, but I didn't want to damage him so I sacrificed a Tracks instead. The final result is pretty rough, but that's fine for me because it's on the rear of the legs and it's just for display. If you want to do a cleaner, more professional job I recommend using a Dremmel to finely grind and shape the parts, rather than hacking away at the plastic with a pair of pliers, which is what I did. You might also want to add a lick of paint to cover up the blue plastic.
Took about an hour to do.
Anyway, I posted the pics here:
http://toybo.blogspot.com/2011/05/wheeljack-leg-modification.html