No need for awk, you can do it with bash:
function find_suffix_head {
find "$FROM/$DOCTYPE" -type f -name "*.head" | while read filename; do
filename=${filename%.head} # strip suffix
filename=${filename#/var/www/templates/testdoctype} # strip prefix
echo cp -f "$INSTALL_PATH/$filename" "$PKGBACKPATH/$filename"
done
}
From there you can just run the cp, too, rather than echoing it.