My $.02
I think you will need a diode on the alternator exciter wire regardless. All of my early Motor Manuals for Chevy cars show a diode either connected to the alternator or on the exciter wire. If you do not, the exciter will will feed back thru the ignition switch and you will have run on, just like I did on my '62. Radio Shack has them for under five bucks. Just get the "biggest" one they have like I asked for (as you can see, I am not an electrician).
