Changing the spring would do more good then just fitting right. The ride quality will vastly improve going from a 1 ton spring to a half ton. You might find the half tons are still to stiff and will need to soften them up some more.
I can see your problem, on one hand you have to open up the axle holes wider, on the other you have to change springs and hangers.
The axle seems like the logical choice, but in the end, its still going to be a 1 ton with a 1/2 to load limit.
I would really look into the spring change, I think you will like it better in the end.
If you still want the axle holes opened up, go get a carbide bur (rotary file) and chuck in your electric drill and have at it. It won't take long, just be sure to wear safety glasses.
Joe
