I'm normally a very safety conscious fellow. Well canoeing, riding my Harley, wheeling, hiking dangerous places..............caution is normally on my mind. Running chainsaws, bush-hogging the lower pasture, etc, That's why I'm so shocked I suppose! Yesterday, I installed a MSD ignition that I bought to go with my Blower. It retards the timing as the boost comes up to prevent detonation. Set the timing and new plugs, gapped of course. Well, now it was idling to fast, since it was running more efficiently. So, I want to set the idling down quite a bit. It did about 10 miles an hour at idle when I test drove it. I don't have parking brakes yet, rear Caddy brakes but no cables hooked up yet. I get "one" chock and proceed to lower the idle. The choke is keeping the idle up now so I just barely blip the throttle linkage..............................OH $HIT! It jumps the chock, knocks me off a 10 gallon bucket I'm standing on and heads toward my parts truck ('82 K-10). I tilt my head back so the mirror misses me, I'm pressing my back hard against the '73 K-5 hoping the rear tire misses my feet! They do, and as the rear bumper passes me I chase the dang thing, jerk the door open and reach for the brake pedal just as it comes to a halt, rear tires spinning in the gravel (rear Detroit). Switch it off and dread looking at the damage as I walk around the front. Hot dang! It stopped about a foot short of the K-10. The 10 gallon bucket got jammed against the front axle slowing it enough so that when it ran over a cut down 55 gallon plastic drum I use for cleaning parts, that stopped it! Only damage ended up being me bucket and me nerves. Post script: I now have two chocks made out of chain-sawed railroad ties as well as more respect for the torque of a SBC!!!!