K-codes had no unibody pieces that were different than non K-code cars. Maybe you can show us a picture of what you mean? As far as I know a K-code was just an engine package sharing the rest of performance package with A code GTs...as far as I am aware the only unibody difference between a GT and a base 6 cylinder car was dual exhaust reinforcement panels. There were plenty of engine, steering, and suspension differences of course.
Here are the differences between the GT / k-code rear frame rails. The ‘reinforcement’ being there to prevent the frame rail from being crushed while tightening the bolts for the dual exhaust. Another site said to modify the new frame rail to include the original reinforced part.
Yes ,only difference is the crush reinforcement inside the rail ,if you have the original pieces remove them from the old rails and insert them into the new rails .
It does seem like i saw someone re making those reinforcements but i cant recall where
Makes me wonder if Ford had issues with the weight tearing through the frame rails. If I had known of that difference during my restoration I might have added them myself....but I do wonder why they didn't have them for the I6...the I6 muffler was huge and heavy and also hung from the frame rails...no crush sleeves there.
6 cylinder and 2 .V cars have a flat reinforcement plate spot welded to the frame rail where the exhaust hanger mounted ,i dont think i have ever seen one crack or tear through . The duel exhaust cars had the extra reinforcement inside the frame rail to keep the rail from crushing because of the through bolts