The guys doing the surveys were archeologists who's knowledge of railroads and logging consisted of little more than that it used rails. Of course they would not consult with the people who did know for fear they might take something. I was friends with some of these guys, but they have a totally different mind set. When we were laying out a new road we were sometimes told we had to avoid a certain site, but were not told where or what it was. What this is leading up to is that it is seldom possible to tell what an artifact is from their description. I know of a flat car that was described as a "machinery frame". Another "machinery frame" appears to be the log foundation of a skid house. At that site they totally overlooked the remains of what was obviously an oil house.
I don't remember finding any rail braces out in the woods, and doubt they used them much, but I did find a gauge rod once. Perhaps that is what they mean by a "rail clamp". As far as a wheel chock spiked to a tie, it could be a derail used where a logging spur connected to the mainline thought I doubt they would have left one of those out in the woods.
I heard once that they had an oil headlight locked away some where, but I could not get anyone to confirm that they even had it.