mini spool or welded. if your gonna weld it, mark the bearing caps and take out the carrier, way easier. also post welding, a trick I have used in the past is once done, bury the diff in a big bucket of sand. it will cause the case hardened gears to cool slower, not effecting the structural integrity as much and giving you a stronger carrier. just make sure you thoroughly wash teh diff in a parts cleaner when done, I also replaced the carrier bearings since sand will get in them.