Havinfun is what I was doing with my 65 last year.It's been a while since I've been here which doesn't say much cause I didn't do much when I was here. If your are still checking this then give it a try. As far as a gas additive I use Marvel Mistory Oil. I think I used 4 or 8 oz. per tank. What ever the label said I think I did. Comes in a red can and not available in some places in the US. An old volvo mechanic swears by it and that was good enough for me. Any way my old 65 was a barn car that got a quick fix and put on the road. I lapped a few valves after the first 800 miles. It was to balance the compresion. The next 30,000 miles went pretty good. Very little valve seat wear. You can tell if they are wearing if your loose valve clearance. If the cam is going then you would have to tighten the valves. As far as octane, reg works just fine for me. My compresion was off and wanted to put new window seals in so the car got parked. I'm not planning a valve job but want to check them and for the most part just lap them.