4. clear ID lights
Most Mk 21’s had several whip antennas installed. Three on the bottom and one topside and others, including this particular plane, had an aerial lead from the fin to the rear of the canopy. I’m in the process of installing these now.
I also discovered, after the fact, that those three ID lights on the bottom rear of the fuselage were not tri-colored as other modelers have called out for, but actually clear. So out came the Windex and a Q-Tip and the problem was solved. Onward to the finish line. I can see it now.