Rich... Glad you found all of the debris in the engine. Luckily it looks like there was no damage...
You may want to consider some screens epoxied over the oil return holes in the heads and lifter valley. Hopefully, nothing like this will happen again but if it does the screen will keep the majority of the debris out of the bottom end.
What pre-load are you running on the lifters?
What spring pressure, seat and over the nose?
Usually, when you start snapping those plunger retaining clips you are having separation issues in the valvetrain due to not having enough spring pressure. Spring pressure is usually not a bad thing compared to too little spring pressure. I have run 250 on the seat and 500 over the nose with an all steel valvetrain turning 8700 rpm with hydraulic rollers. Although, it was with some "trick" valve springs... A buddy of mine runs 300 on the seat and 650 over the nose with 1.540 dual springs, factory Ford hydraulic roller lifters - not "shimmed up" either - and turns 8900 rpm. He usually changes the lifters out after 150 passes just "because". Of course, these are drag race set ups. I don't know how they would hold up to road race abuse...
