There are several things that can cause pinging: timing is #1, lean carb, cam timing, engine heat, I may think of some more. The first thing to do is retard the timing before you chew up you pistons, that'll hurt. I advanced my 85 CJ7 until it pinged and then backed off a little. I'd replace the thermostat with a 180 degree to cool the engine second. Then I'd start on the carb. How does it idle? How far is you idle adjustment screw turned in. Cover the throat of the carb with your hands, does the engine speed up. That is a sign of a vacuum leak (lean carb). Cam timing, did anyone change the cam?
You need to figure out your initial advance, vacuum advance, mechanical advance and your total advance. Sounds like your first purchase is a dial back timing light.
1985 CJ7 - total customization underway, Sublime green and Plum crazy purple, Ford 9", 258 w/ Holley 475
1985,93 CJ7,YJ - L98 TPI Vette motor, Atlas twin stick, Dana 60s front and rear, Arbs, 39.5 Swampers