Actually I think that might be right. It appears there is a lever on the engine and if you replaced that one with the orange one and then mounted the angle bracket to the two outside bolts for the compressor/fuel pump drive it should work.
As I recall the lever for the compression release is not keyed to the shaft, seem to recall there being a dowel pin sticking out the front of the block that limited the stroke and a slot in the end of the shaft to let you adjust it in the lever. Have an old NH book that briefly shows and mentions the compression release but I can not see any adjustment procedure for it.
For lack of any spec's on adjusting it I would install the arm loose with the "return spring" holding it to the left as you face front of the engine and after setting all valves turn shaft clockwise till you feel it touch the collars on the push rods then turn back counter clockwise a touch for clearance, again this is looking at the engine from the front.
The release only opens the valves a very slight amount just enough to bleed off compression to let engine turn over easy.
If you look at the back side of the lever you might see marks from the dowel pin that should be a little.
Picture below has red arrow pointing at the dowel pin mentioned above and shows the slot in the end of the shaft, green arrow.