Rear Axle questions

[Charlie46]

I have a 2000 XLT 4x4,CC, LB completely stock with 280K on the odometer. I've been getting what I consider excessive rotational play in the rear pinion and am planning to to give the axle a rebuild this spring. In prepping, I learned the axle is a 3.73 non-limited slip axle (S406H according to the tag). I've also located a few 3.73 limited slip (S409H) axles on fleabay (these seem to as rare as hen's teeth in the PNW lately) and am considering buying one to rebuild and upgrade the truck a bit. Has anyone else done this swap? Pitfalls? Alternately, can the S406H be converted to a limited slip axle? Has anyone else done this mod to a 406 axle? Pitfalls? Thanks in advance.