LOL ive got the mig but not alot of scrap angle, seriously though, alot of good suggestions here but one that might work too is use a torch and braze the end plates on, brass can be run on the outside and with the right heat, would fill any voids in the joint. and as a plus, brass is softer, so if necessary, the inside of the joint could be smoothed out with a dremel, or something similar
one thing i think would be wise, is be sure to heat them red hot (prior to brazing if that method is used) to remove the scale from the iron so you dont get needless contamination in the ingots