on the early cars the coil was mounted either on the intake or on the head near the dist. heat does reduce the life of the coil, but that is not why they were located where they were. the location reduced the length of the coil to dist wire reducing reisistance in that wire, thus allowing more spark energy to reach the plugs. remember that the stock ignition systems of the day were not that energetic, compared to stock ignitions of even the mid 70's, and thus the less resistance int he coil wire the better.