Dan,
I don't know of one in OK so can't help. I would recommend you talk to a local or OKC Cummins authorized dealer. Determine if you like their attitude and prices.
It's not very close but I live east of Lubbock, have a large 42' by 60' steel barn, and a friend who was a Dodge dealer tech at a local Dodge dealer for six or seven years. He works on Volvo industrial equipment now but still does an occasional major repair for friends evenings and weekends.
If you purchase a new Cummins reman or a low mileage take out from a wrecked same year Dodge and transport your truck and the new engine to my farmhouse in Crosby County I could put you in touch with my friend to have him swap it out. He is honest, reliable, and does good work at very fair prices. He has done all my work for about seven years. My suggestion would not be the easiest to put together but could be a fall back position.