If you lock a 20, you'll be replacing the two piece axles very soon after.
If you want to weld it, you'll need an open carrier with spyder gears.
If you want to lockrite it, you'll need an open carrier.
Or you can just rebuild the traclock.
Wayne @ Big Island RockCrawlers
"PYRO" The Rock Crawler
Web Site: http://www.members.tripod.com/surfmac/Index.html