Whats your compression ratio? Pinging can be from too much timing, or too little octane for compression ratio. You running high-octane gas? Rule of thumb is the octane you need is 10 times the compression ratio. If you've got 9:1 compression, you need 90 octane gas.
Timing should be set with vacuum advance disconnected and vacuum source plugged. With motor at slow idle, set base timing for about 10 degrees BTDC and see how it runs. Is your advance mechanism free, lubed and working correctly? The mechanical advance mechanism is what controls spark advance above idle. Too much and she'll ping and detonate, to little and she'll run like crap.
Petronix is a replacement for points. It fits inside the stock dist in place of points, and uses a magnet and hall-effect sensor with signal amplifier to trigger coil. Costs about 80-100 bucks for the system, hook up 2 to 4 wires and go. I've got one in a 235, and its great.
