Those shafts look like they are from a stamped steel set up. You can tell by the large oiling holes. Adjustable 273 rockers have 2 oiling holes per rocker on the shaft. One near the loaded side of the rocker base (Should have a banana groove, but they all don't) and one to feed the rocker adjuster with a dribble amount of oil as the rocker moves up and down (timed exposure).