I'm not sure what O rings you are refering to. The intake runner O rings are a #123 and getting them in Viton or Silicone would be your best choice. But there are only 6, not 16 O rings. These are at the intake runner where the tube meets the cylinder head.
Not those. I have plenty of them on hand. I get my o-rings local at a real good price. The ones I'm talking about are the o-rings that deliver fuel to the carbs. I was hoping it was a fuel line, but yesterday pulled the tank and rigged up a gas bottle so I could see the leak and it was the o-rings on the right carb bank where it tee's between #2 and #3 carb.
David