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"??????
It ain't rocket science!
'Course if yer house has more wheels than yer truck...
" Old age ain't for sissies "