Shortening a Ford axle

   I'm shortening an axle to replace a damaged one in a one-off Gold Wing powered FrankenTrike . The original axle assembly came from IIRC a Ford Pinto (or Maverick maybe) , modified for the trike . The owner's son got a little too heavy handed on the throttle and lost control , ended up in the woods and partially wrapped around a tree . Bent the axle flange and cracked the weld where they cut a piece out of the axle .
   So I've got the replacement cut down and almost ready to weld back together . I was going to MIG it with ER70S6 , but I'm wondering if I should TIG it with some ER309 or 308 . It's I think a carbon steel , it sparks orange with short forks - and it's hard . I started out with carbide cutters but it was pushing the axle out of alignment instead of cutting . Since axles apparently aren't exactly straight (!!) I decided to turn a couple of reference bands so I can check runout and have a concentric band to mount the steady rest , ended up using my Dremel as a toolpost grinder using reinforced cutoff discs . That worked out well . So now I need to decide which process and filler I need to use to glue this thing back into one piece .
--
Snag
  "They may take our lives but
they'll never take our freedom."
  William Wallace