Regarding the condenser and different distributors - it has more to do with the coil and point gap than anything else. A capacitor (condenser) is a storage device. It does not pass current and to DC it is an open switch. Apply AC (in the case of a distributor it is actually pulsating DC) and the condenser (capacitor) looks like a closed switch. The higher the frequency (pulse rate) the less impedance the condenser has. As you speed up and contacts open and close more rapidly, the DC pulse speeds up and the condenser has less and less impedance. The purpose of the condenser is to prevent the points from arcing as they open and close rapidly. When the points close, they ground the primary side of the coil and it builds a magnet field. When the points open, the magnet field collapses and induces a current through the coil in the opposite direction. Instead of this reverse current arcing through the points to ground, it sees the condenser as an easier path to ground, hence bypassing the points and preventing an arc. Given the variance in the rate at which the points open an close, a few microfarads probably won't affect the operation too much. A different number of windings in the coil will affect the rate as well but again, probably not enough to notice and the worst that would happen is the points wear out a little sooner than normal. Now, having said that, a shorted condenser will certainly prevent a car from starting as 324darrin describes. Some times heat will break down the "plates" in the condenser causing them to disfigure and form a short circuit preventing the car from starting. The condenser cools down, the plates inside it retract back to normal and the car starts right up.
I had it happen with my '51 Kaiser a couple of years ago - I'd drive it around and it would start missing, blubbering and eventually die. Let it cool down and it started right up. Drive it till warm and same problem. Replaced the condenser and problem has not returned. I never had it happen due to short periods of the engine being shut off but I can see where it could produce that symptom as well.
