Free cam build...

I built a similar motor a few years ago for a local bracket racer.
He bought a used set of RPM heads, and had some used Crane iron rockers, an 850 Holley and a 340 block, and I built a motor around those items.

To help insure there wouldn’t be any issues with the rockers galling on the shafts I used a cam with even slower ramps than the OP’s Crane piece.
I built a 12:1 416, Scat cast crank & I beam rods, and Pro-True forged pistons.
With a little tweaking on the heads, SV intake, his 850 carb and a cam that was like 265/270-106, .560 lift....... tested with 1 3/4 - 1 7/8 x 3 dyno headers it made about 560hp.
Ran 10.70’s in a Dart.