Ran my Tall deck well over 3500 many many times and NEVER came apart once.. I had 18.5 tires under the back end of my 57 chevy and 320 gears, It would fry the tires at 45 mph,, Would I do it again.. Sure if I had to,,That car was very fun to drive,, And I DROVE IT HARD !!!!!
This mark on the black top should let you know how well they can be...We marked it off at well over 150 feet before the car got side ways..
But did you keep those heavy 4-ring pistons?
What I see happening is one of the same problem the 409 had: The weight of the pistons would pull the big end of the rod apart if you ran any kind of rpm with it