Failed LS7 4 times

[Flatblack 57]

I am on my way to a new 540, but still do not know the reason the old ls7 failed. This motor was rebuilt 3 times since I have owned it, each time with oiling problems. First it dropped pressure, on the dyno, and spun mains. Second it lost pressure, nearly seized and the strip down reviled jammed lifters. OK, block is not indexed and that must be the prob. Third time after 20 mins first start up, system 1 filter shows bearing metal. Strip down shows slight ware on mains again and crank scraped. Each rebuild done thoroughly, cleaned, and put together with basically all new parts except crank and block. What the hell is going on. Three engine builders can not find the problem. I only hope it disappears with the block and the crank