I've never even had one apart, but from what I could tell from the IPL, you don't have the room for a weld bead, on accountta the fit up into bushings etc.
I saw the price on the IPL.
MIG, stick, tig, whatever, yer still gonna end up with a bead that will interfere/rub against the faces. Ya might could use a die grinder to put a heavy countersink in the gear I.D. in which to lay yer weld bead, then grind it smooth.
Really depends on your skills.
WTF is "pig metal"??????