Measured and documented lengths of the original aluminum flap pushrod assemblies. Cut new 4130 steel push rods to 5 inches, which is 1/8 inch longer than the aluminum ones for more thread engagement for the rod end bearings. As with the aluminum rods, I chucked them up in a disassembled Rolo-Flare tool for drilling and tapping.
I drilled both ends of one rod to #3 one inch deep. Tapped one end of one rod 1/4-28. The steel is MUCH harder to tap than the aluminum, so I could only get the tap started while chucked in the drill press. I finished by clamping the flaring tool with the tube installed in the bench vice and turning the tap with a wrench. This was a rather tedious process, as I could only cut about 1/4 turn at a time before having to back up and break the chips. I used Phillips 20W50 for cutting oil.