Exactly! What ever oil you use make sure its got Zinc in it and specifically spells out for V twin use
I may be wrong, but I don't think you'll find many V-Twin rated 20-50 oils with any zinc. For flat tappet cams and braking in motors, zinc seems to be the requested product, but I wasn't aware that you needed to continue to use any oil with zinc additive.
I believe that zinc is not EPA friendly. Regular API oil is limited to 800ppm zinc/phosphorous and diesel oil has 1200ppm of zinc/phosphorous.
One of the highest load areas of the S&S motor is the valve train and they use roller lifters, so there is not a lot of friction.
I've used Amsoil in my Harley, I've used Mobil 1 and most recently Liqui-Moly 20/50 Harley oil. This oil is made in believe in Germany so it should be available for most of you guys.
I think I'll use Liqui-Moly again on my next oil change.