Breaking Flex plates

http://www.robbmcperformance.com/products/dowels.html

I use these. If you're breaking flex plates, you definately have a problem. What exactly was done to the engine to build it up?

Nothing out the norm...360 heads, a decent cam I thinkin maybe an rv type. When it's runnin people always ask is it a 340.....727 shift kit 2500 stall. Right now the car sits most of the year. The first time it break I had come stateside and I drive it from Danville to Richmond...Went to Wally World, came out catch second come to the stoplight and I hear it start to makin noise. Replace flexplate wit one from Advance Auto...Looked "beefier" than what I pull off. Put it on...Couple months later I come back drive the car....Catch second and come to the stop sign an hear it doin it again......I hope that helps out....Oh yea I shift round 5100 5300 rpm...Nothin to high......