[dsraven]

when I boxed the original frame on my 57, before I did a frame swap, I simply went to a fab shop and had them shear me some 3/16 cold rolled to fit the width I needed then cut off some areas to fit the down taper etc. just be aware of how the plate will fit to the original frame and leave room for the weld bead. I cut the plate narrower than the frame width by about 3/16 top and bottom so there would be ample room for the bead. I used magnets to hold in place as I tacked it all together. remember when you weld them in to just weld a short piece at a time and then go to anther cold spot and do a bead kinda spreading the heat of welding out everywhere. don't go back and carry on with an old bead unless that spot is room temp again, like you would feel comfortable sticking your tongue on it (ok, yukk, but you get the point). otherwise all your work will be for nothing because the frame will not be straight anymore. you would be surprised how much heat stretch and contact rates can bend a frame. another thing I do is cut the mig wire before every weld start to ensure a nice chisel tip and easy start for the weld and also I grind back with a grinding disc on edge, about 1/4", on the end of the old bead that i am welding onto, this ensures a nice clean add on bead plus allows you to check your old bead for contamination porosity etc.