383 rebuild - kinda whimpy on the dyno?

Exactly. I don't think the builder was doing anything more than weighing cost vs reward.
I've watched the stamped steel rockers flex and with any real spring and an aggressive lobe. You can see it turning it with a socket, nevermind at 5K rpm. I see valvetrain issues on that trace/result.
I’ve seen them more than flex!
Comp Xe275hl

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