I need to install a new header to enlarge a window (in a load bearing wall).

I was always under the impressing that kiln dried lumber, instead of green
lumber.
was the only way to go when altering existing construction, to avoid the
problems
of shrinkage.

As far as I can discover, only green lumber is available in New Jersey for
anything
larger than 2 x 4's.

I am particularly concerned that the ceiling, which is supported by this
header,
will crack over time, as the new header shrinks.

Am I worrying about this unnecessarily, or is there a technique of
installation
that avoids the problems of shrinkage?