Stepped planes as a reference

[[Gr...]]

I have a casting where most of the GD&T callouts refer to A-B. Datums A and B are planes that are parallel, but offset by 5mm. A and B are both large machined surfaces, offset by 5 mm, have flatness callouts, and need to be scanned. I need some help with the best way to implement the callouts in a meaningful way.
Also, sorry I can't show pictures of the casting.

[[Da...]]

Gregory, I would do it this way probably. Note I haven't tested this anywhere and shurely someone here will jump in with better solution

align1.JPGdatumA-B.JPGoff.JPGB.JPGA.JPG

[[An...]]

See attached.

Contribution_12_03_2019.pdf

[[Da...]]

Very nice idea, Andreas.

[[No...]]

What we usually do in such a simple case is to probe the (few) points of one of the planes as single points, then recall each point to another point and modify the rrecall formula of the offset direction (Z here) so it adds the desired offset. Then we recall the offset single points together with the points of the other plane to one common plane. The whole thing is then repeated in an iterative alignment.
Of course this only works if you have only a few points.

[[Gr...]]

Is there any way to combine Norbert's and Dane's ideas?
Dane's 'offset then recall method' leaves out outer tangential considerations, and Norbert's 'recall individual points with an offset' would be really difficult with 500 points.
Both methods are helpful, and I will remember both for future use, but do not get me all of what I need in this particular situation.