Found the Australian rules online,and will have to
assume for now that they match the Americans.
5.7. Chopping:
The removal of metal from a body component in such a fashion
as to reduce the overall height of the component without changing
the shape at top or bottom.Tops must be widened and/or lengthened
to maintain the stock silhouette of the vehicle.IE: No laid back windscreens.
5.9. Contour.
Contour is the configuration of the external sheet metal.Removable trim,lights,windows,floor boards and interior sheet metal are not part
of the contour.In the special case of chopped tops,contour is considered
to have been preserved as long as the angular relationship of the top to
the body proper is not changed.
6.3. Modified Category
This category encompasses coupes,sedans,and pickups(with full stock beds),
unaltered in height,width and contour,and with all the stock panels mounted
in original relationship to each other .......
I think 5.7. answers my question.
"Tops must be widened or lengthened....".
So it sounds like for /CC,the angle of the rear,and side glass,
should be stock,relative to the body.
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The Ghia has no B-pillar,but it's easy enough to
project a line for alignment purposes.
The jury is still out on the motor choice.