340 and octane

I also run a 340 with the same heads with a little more camshaft. you're might be fine but you're probably walking The Razor's Edge. that's a big Maybe and a chance I would not be willing to take. I would invest in some good octane boost and have it on hand mixing your fuel up to at least 92. Just because you got away with it one time doesn't guarantee that you always will. Lug the motor down or get your timing wrong and pay a severe price.