I expect that few or none of these cars were repainted/relettered for
GM&O. The Alton series was almost entirely retired/scrapped in the late
1940s.

There are a few photos showing these cars in their Alton days. Page 6 of
Ray Breyer's Alton fleet summary shows another 17000 series rebuild,
albeit with the original (?) roof and inverse Murphy ends. This view
does show the extended side straps and the door setup.
http://designbuildop.hansmanns.org/wp-content/uploads/2021/10/Alton_frt_car_fleet.pdf

Several of them show up in this view:
http://www.idaillinois.org/utils/ajaxhelper/?CISOROOT=p16614coll63&CISOPTR=6617&action=2&DMSCALE=100&DMWIDTH=9999&DMHEIGHT=9999

David Thompson