I would go with the internally regulated alternator especially if you are going over 90 amps, it will tidy up the wiring and simplify it also. Run relays as mentioned, they can be hidden, so that little load is being put on the older components in the cabin. If going with a loud stereo system then you will have to run all new wires to suit. You might consider bridging out the amp guage also as you really don't want 100 plus amps flowing through it if the system needs it. Remember the alternator will only put out the amount of current that is needed at the time, not max output all the time.