Ok if your going to do this you first need to know what type of bars you have, Laminate bar or Solid bar, both have to be the same. I suggest tig weld because you can control the heat better and reduce warping better. The best way to weld is lock the bars in a vice about half way down the bars and tack weld both sides in 2 or 3 places, remove the bars and grind welds flat the put the bars back in the vice and tack weld the lower side, remove from vice and grind flat. Put the bar back in the vice and weld one side then the other, alternating from side to side as you weld, take your time to allow heat to disperse, leave in vice till cool then remove and grind flat, turn over lock in vice and do the lower side of bar. You can re-cut the chain groove with a dremel tool