Hickory BBQ Sauces for Hamburgers

I was raised in Oklahoma City and was weened on the hamburgers from Split T (now gone), Charcoal Oven and Johnny's, and have been trying for years, now that I live in California, to replicate the wonderful Hickory Sauces that they put on their hamburgers.

In this, I have been unsuccessful, and was wondering if anyone has:

1. Had the hamburgers from any of these places, and know what I am talking about, or

2. Has some homemade recipes for this type of sauce, which is a sweet tasting, hickory smoked sauce, and not too spicy, and is really not a true BBQ sauce.

I have even called a couple of these places, and asked about franchising out here in California, but to no avail.

Thanks for any help or suggestions.

Homesick for OKC hamburgers in California!!!

Split T