1969 Slickback

I considered doing this to mine, but the driver side was way too bad. Overall it was less work to do what I'm doing. Is that your car? That's a good idea using the k-member to set it up on. I presume they positioned everything and then simply positioned and welded.
Yes that is mine. We did it that way because the front clip I picked up was cut before the torsion bar cross member. I happened to be wandering through a yard one day and ran across just the front clip, dash forward laying there. Apparently someone had wanted the floors so that was how it was cut. We measured, clipped it back and welded sleeves inside the existing frame rail. Then slid the new ones on, bolted to the k frame and did some cross measuring to be sure everything was as it was before cutting it up.