1972 Duster Build with my Daughter

That K frame, id get a big enough plastic trash can w lid to submerge it completely, and mix up feed grade molasses and water 9 parts water to 1 part molasses to fill that can up. Attach wires to it, and submerge it in the molasses for about a weekbor 2, then hit it with a pressure washer, it will be clean as a whistle. With nice bare metal

Then before it has a chance to dry and flash rust, spray it down with tri sodium phosphate and water solution. You can get the TSP in powder form in paint dept at lowes or home depot.