383 rebuild - kinda whimpy on the dyno?

my point is- I don't think that's the true peak, since it wan't tested any further.

What does the RPM range of the cam card say per the MFG?

If the OP is not satisfied with the power, he can either adjust the "peak" downward or extend the RPM range upward to see if there's any more on the table.

Potentially without replacing any parts.

see how that works?

I do. Nonetheless, it's an "underheaded" engine. That cannot be debated.