67 Cuda: disappointing dyno numbers, need some advice!

The other way to approach it is...... have a couple springs tested, and(if they’re suitable) swap to a longer duration cam that will work with whatever they are....... and not buy the new rockers yet.
Cam swap & a manifold.

I def wouldn’t go to the trouble and expense of rockers, pushrods, and springs without upgrading to a solid lifter cam.