I did the milodon oil pan on my 66 Dart and I had to notch the k frame. The pan would fit in but it was to close and when accelerating would have hit. Heres a pic of my k frame once notched.
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I added the gussets in the corners for extra support. The gussets are all the way to the rear of the frame then built the fill in around them. If you need more pics let me know. I have plenty of clearence now.
Rod