Alternator regulator ??

I am over hauling a 79 ski nautique with a 454 merc. I am down to the charging system. Right now the set up is a one wire alternator with a external regulator. I am not sure if this one wire alternator has a built in regulator but I am assuming it does not. The system looks as if it originally had a three wire alternator but I am not positive. I am not sure if I should go with a three wire alternator set up or a one wire set up with a external regulator. Is a internal regulator better then an external or are they both the same. This boat has been changed around so many times I am not really sure what goes where but I am getting it together. I have a 1000 cold cranking battery. What Amp should the new alternator that I buy be? I dont want to start putting in 3 guage wire and all that for a 135 amp alternator.

I changed my 3 wire to a one wire and use the solenoid on top of the starter rather than the remote. Very neat wiring and it's run well for a year now.