not sure - somewhere between 1/8 and 3/16 - it was one of the commercially avail repair plates and i ordered it with the brace that goes to the center of the crossmember under the radiator.
it was not a question of bending the plate to the frame- the contour of the stamping was incorrect to mate up to the box itself. I torched it, beat it with a sledge, looked at it, torched it more, test fit it, ripped it off, torched it, cursed a little, tried a smaller hammer, tried both hammers from the other side... anyway you sliced it, there was going to be be problems. thought about trimming it down and seeing if it would fit on the INSIDE of the frame rail, and then modify everything else that is in there with it, but it would have been WAAAAAAAAy too much work, and I ended up aborting.
I'm just glad I caught it before welding the stink out of it and having a permanent problem with my frame afterward. looked like it was going to impart all kinds of stresses on the original frame, and there would be no way to use the scab plate without cutting it up into little pieces and doing a hell of a lot of grinding and test fitting.
I ended up drilling holes on the ends of all the cracks, then grinding into the material, welding, and grinding down the outer welds down to the original surface height where the box needed to fit. then i used the bolt on brace on the inside.
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