I've had 2 engines with OE 360 iron cranks. 73-7500 RPM. One was tubed, the second was bushed. The first spun a bearing and broke the rod with a low run count when I didn't pay close enough attention to it. The second one was constantly trying to do the same thing. It would hurt one bearing in 7 or 8 runs, same one everytime. If it was bad we would check a second rod, again same one everytime and usually replace it. Tried a lot of things before we got it reasonably under control and was able to go a season (120-130 runs) without fixing the bottom end. Above about 6800-7000 is when it gets to be a problem and oil system mods are needed, in my experience. Maybe others have had different luck with them.