If you ever saw Warped Perception utube and the beating he gives his, you won't need any break in oil. ZDDP is just for break in purpose, used it on my spitty.
Still can't imagine it lasts very long, even with the zinc. At least the plastic ones have a hard chrome coating. I work with metal all day long and have for decades. Either you weren't putting out the ponies you say, or you're not telling the whole story. Maybe a race or two they be fine, but your rubbing a piece of metal on another without a harden spot. It won't last long, idc what anyone says, I have 30 years of metal behind me and billions of dollars of industry studies to back me up. I just can't see it lasting very long at all. Maybe a race or so, but not long term or reliable.
The cam isn't the issue with those little engines, you'll float the valves before any serious wear occurs. Pull the cam and have it nitrided and get some strong valve springs to fix.
Most tanks don't fit an OCC anyway. Maybe a monkey bike tank, like I have on my XXXX bike.
Do you have a flat head? Prop it up in the frame and take a picture, but I'm fairly sure they would look great in there.
We love pictures here. We really do, the more the merrier.
You can have quite bit of tilt on the flathead briggs, the old vintage flathead race carts the engine tilted something like 20-30° degrees foward, if my mind serves me right. The flathead is a old work horse & hard to beat. A predator type engine would probably fit easier for you, but I think the flatty would look better.
