I would contact Dale Chlouber at the Washington Irving Trial Museum located at 3918 So. Mehan Road in Ripley, OK. Phone (918) 624-9130 or by Email at Cchlouber@aol.com. He can pin point your request to the Dunn ranch location for you.
Thanks to everyone who replied, I really appreciate the info. I used to live outside of Stillwater and have spent some time in Ingalls and the surrounding area. I've driven the section roads east of there hoping for a clue where the ranch might have been but had no luck. I saw a web sight yesterday that said it was about 15 miles east of Ingalls. Has anyone been out there and found it? I also have heard stories of a cave overlooking the Cimarron River that served as a hideout/meeting point for the Doolin Dalton gang. Does anyone have any info about that? Thanks again