I don't know why Mopar Performance ever coined that term "constant output". With the exception of some late model cars where the voltage regulator is part of the computer and they control the ouput of the alternator based on ambient temperature I have never seen a voltage regulator that wasn't a constant output.
Any, back to your question if your charging system is keeping up with the addtional electrical demand of the MSD and fuel pump there is no need to change anything. If it isn't changing to one of the MP "constant output" regulators won't fix it.
Don't know what vintage your car is but if its 60's vintage and has a vintage regulator it is going to be mechanical. You can purchase a drop in replacement from most any parts store for $10 or so that will have electronic guts and will work better than a mechanical one. But if your electrical demand is greater than the rating of your alternator then you will need to upgrade it and likely the wiring too.
