68 Dart Project.
You are likely already doing this, but to gain a little work room when installing the steering box w/ header in place, try lowering the k by loosening the K frame bolts to the max allowing the K to drop an extra 1/2" or so. Once the steering box is installed (header already bolted up) re-tighten the K frame bolts.
......the difficult gets done immediately....the impossible takes a day or two.