71 Dart get 408/ Trick Flow Heads....

I’m pretty surprised at how thin the bottom of that lifter is.

Look how cupped this one is...... still no big hole in it:

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I’d be tempted to take a cutoff wheel to one of the remaining “good ones” to see how thick it is to start with.
Aren’t the Howard’s edm’s essentially a reworked hydraulic lifter body but with the solid insert utilizing the same snap ring location ?