AFAIK there hasn't been an upgrade for this roadcourse. First,last and foremost,this NOT an historical upgrade but simply an attempt to provide some higher resolution textures. The default track contains generic tree textures from the original Papyrus tracks and IMO they probably aren't realistic either,nor particularly pleasing to my eye. I've tried to match the kinds of trees that would be more likely to be seen at this central California coastal locale from what was in stock at the Repository.
The original horizon by Simon Stobbert for Watkins Glen is a fine one indeed but really doesn't depict the area around the Monterrey Bay area and IMO the one included by Scott is a pretty good overall representation. The Repository gets the credit for all these textures and I'll take the blame for their useage. Someone had to be the first test mule to try something like this and it just so happened to be me. YMMV(Your mileage may vary)so just send this update to file 86 if dissatisfied.