Very bad idea, it will not last long and you will need to replace the entire rearend after it blows up. But if you really want to do that you weld the spider gears. A minny spool would be a better way to go, chech summit or jegs.
:-& If all you want to do is drive in a strait line, go ahead and weld and while you're at it weld the steering knuckles so you don't get tempted to turn :lol:, but e prepared to pick up the pieces when you snap an axle or tear up a tire. Better yet, buy a carrier with posi in it and replace the one you have. Check out Jeff's Bronco Graveyard or LMC Truck.
If you want to get REAL picky, Posi is the generic term applied to the types rear ends that do some sort of locking, the other terms describe the method of locking.