The MSD unit will be fine. The "Potting" that protects the intrenals of the MSD box helps disipate the heat through the aluminum box itself. I can't imagine too much heat being conducted by the mounts.
Regarding the distributor removal. Note where the rotor is pointing, if easier rotate the engine until the rotor is pointing directly to the front, side, rear etc. While removing it slowly twist it back and forth to prevent from pulling the pump drive out of the pump. After spining the pump with a drill reinsert the distributor so the rotor ultimately ends up pointing in the same direction as when removed. You may have to turn the pump drive a small amount before the distributor will slip back in easliy. Once you get the hang of it and see what has to "line up" it becomes easier. I do this each time I change the
oil.
Rick
Rick