I knew I had a pair of Kato ACF 70 ton hoppers sonewhere but as they were CB&Q I didn't want to donate them. Having dug them out (once again, thanks to those that helped me get over the brain cramp) I was disappointed to see they are way, way too dark gray. The CB&Q hoppers were light grey (BLMA has it perfect IMHO) so it now appears I do have a couple of donor cars for either two Westvaco soda ash haulers or maybe just one and add a Kimberly Clark hopper for either soda ash or clay.
I'll take Jason and Bryan's advice and make open side versions of them as the only references I can find are Bowser and IM's HO and O scale models of the Westvaco and KC cars (I know, rule # 1, don't model something from another model) but it's all I can find.....