Assuming you aren't running it lean, you need to look at your mech advance. Or total advance. If you can get your hands on a dial back timing light get it and see where you're at. I fought an annoying pinging problem forever and ultimately found I was putting 42 degrees in pretty quick(by 2-22K) plus whatever the vacuum advance still wanted. I'm running hi grade w/ 9.6:1 compression in a 250 at sea level. Your 200 shouldn't be pinging. The stock setup in my distributor was a 15L on the small weight. That put me at 30 degrees all in, add 12 degrees initial, plus whatever vacuum is available and you can imagine it may hit 50 degrees or more. The vacuum advance can put in as much as 17-18 degrees or more full tilt. I welded the weight and then filed it to a 13L, ie. 26 degrees, and it fixed all my problems with pinging. I had the vac diaphragm turned to full delay to try and help, but have backed that all the way off as well. I also had drilled and threaded a hole for a long set screw to catch the slot on the arm and limit the vac advance to <11. That's gone to. Next step is to put some 87 in it and see what happens. It's still got all the timing it needs to get up to 70 or light up the tires. Find a dial back light and check it out.