Alignment a/b/z

This is a method for determining the Datum point Z using just datums A and B

Measure and align to the datums A, and B

Using trig calculate the PCR of the point Z in your case that would be 157.385

Create a series of Generic points with a PR of 157.385 spaced in the area that the cast flat will be rough located
would suggest spacings of the point of 5 degree . ( note the points must be at the correct height you will need to determine that
as not on the drawing you posted )

Create a constructed curve from the points

Measure a plane on the cast angle face

Construct an intersection point between the curve and plane

Construct a 2D line from datum B bore to the point

Rotate align to the constructed line then offset rotate alignment by 4.0078 degrees.

Have attached a sample program showing the stages in my example putting a point at 25 PCR, X 5.0

HTH