The pinch clamp that attaches the vacuum advance to the distributor housing should be your primary method of setting the timing. It allows the housing to be turned 360 degrees without moving the octane selector away from zero. Here's a simple method of getting the timing in the ballpark- - - - -with the engine stopped, align the pointer and ball by rolling the engine over slowly. Either turn the fan blades or put the transmission in high gear and gently roll the vehicle forward while watching the pointer/ball junction. Once they're aligned, turn the housing clockwise until the points close, then back up CCW until the points just barely open. Lock the pinch clamp screw down. You'll be within a degree or two of the correct setting without ever starting the engine. This is called "static timing" and it's actually the way ignition timing was set before strobe lights came along. A Model A Ford engine has a tapered pin threaded into the timing cover, and a divot in the camshaft gear. The engine is turned until the pin can be inserted into the notch, then the distributor is static timed as I described above. Then the tapered pin is threaded back into the timing cover, with the pin pointing forward. Chevy just does the same thing with a window in the block, and a ball and pointer.
Jerry
