I also had a bunch of lifter failures comp lifters were not up to the task of a spring that's 1290 over the nose of the cam, super charged would have the same affect. I went to full body lifters/keyways and that problem was solved

While the block was being set up for keyway lifters would be the perfect time to upgrade the cam tunnel to 55mm cam bearings.

When I was building my engine, the Competition Eliminator racer I was working with at the time talked me into running the keyed lifters. He said that that the tie bars introduced an harmonic that could cause problems.

Maybe you are seeing an extreme case of this phenomenon.

Have you had the cam out of the block since you put it together and ran it? I would bet my next paycheck the cam is twisted and once you take it out it will not want to go back in. I had similar issues with a big block 7500+ rpm and a 55MM cam core fixed ALOT of issues and made more power. To get that kind of lift a stock cam core is really small. Look at the base circle and think about what that thing is doing with that spring pressure and 7000 rpm. Big cam core and pushrod oiling through the lifter will fix a lot of things.