If you pull out the spider and side gears you can weld up between the gears that mesh, you fill all but 4 valleys on each gear, leaving 2 valleys opposite each other on each gear untouched. Pull your cover off a look at how the gears inside the carrier meash, you will basically weld where the gears aren't meshing and leave where the gears mesh alone, all done on the bench. This way your diff can still turn about a 1/16-1/8th or so of a turn alowing slightly easier steering, the gears aren't all welded together and the carrier is left untouched. I have heard it called a Fozzy locker before.
This method of welding the diff is a lot cleaner as well as easier, for one you have the gears on the bench for ease of welding and you also have the gears on the bench so no slag or spatter needs to be cleaned out of the carrier after welding.
That way if you break a spider or side gear you can pull the chunks out and slap another gear in there a go at it again. Did that make sense?
I have ran welded fronts on several trucks for years at a time, the traction provided by having the front locked with the rear, way out weighs the turning effort involved, IMO. Spool or mini spool is basically the same as welded only slightly stronger, no differentiation between the 2 tires on that axle. When you weld the diff you are essentially making it a big spool.