Just for 'general' interest...
In the 4x4/Rock Crawling world, welded diffs (Lincoln Lockers) are very common, likely more than any other auto sport...this would be my background.
The general practice is to weld "everything to everything" in the carrier for 100% lock, including side/spiders to the carrier itself (eek)
A gentleman from Vancouver Island (Sooke, BC actually) 'invented' a style of a welded diff known as "The Fozzy Locker", whereby the side gears are welded at 12-3-6-9 valley's, respectively. This allows for almost a 1/4 rotation in a corner prior to lock up..and saves on tires a fair bit in comparison to the standard method. He (Fozzy) was meticulous in how the welding was done, with weld, grind and repeat until he was happy with penetration (I watched the process 4 times)
I ran this setup in my 8" Toyota rear diff for 13 years on a daily driver, with 36" tall Interco Swampers.
http://www.offroaders.com/tech/Lincoln-Lockers-Fozzy-Locker.htm For the OP: having it removed is a good idea, as not trusting the work would be my main concern...including reassembly.