I had a huge crack in the middle of my tailgate from the PO running 33s on stock carrier, he tried fixing it with shitty welds, which broke. It was about 7" long from the top/middle to about halfway down.
All I did, used 4" grinder to grind down rust. Drill holes through the actual crack (about every 2-3"), screwed in 1/4 bolts, cut them flush with the tailgate. Pulled out the 4" grinder with sanding disk again and smoothed them out. Mixed up some Belzona 1111, applied generously, on the inside I bolted a long piece of aluminum with belzona applied on one side across the top.
For all of you who do not know, Belzona 1111 is a corrosion-proof, weldable, paintable, Machinable super metal. It can be applied to just about everything. And used in a wide range of applications like engine head repair.
Now I just did this last night, I still need to sand down the belzona and then paint will post pics when I'm done.