Tyler, I can't answer too many specifics about those cars...but there were many different arch bar trucks used on the various narrow gauges. There were at least 5 different varieties on the C&S in 1899.
While those trucks don't look like it to me, Carter Bros trucks were quite common west of Colorado...even in Hawaii.
From what I've been able to find, we are looking at ex-SPng 449 which was ex-SPC #124. She was built by Carter Bros in 1891. I would guess that she is a 28' car. The original trucks, CB trucks, would have had brake hangers and a 4' wheelbase. Railway Engineering offers a similar car for $30 in HOn3. I believe that Rio Grande Models offers the correct trucks for $6 (Carter Brothers trucks). If someone else here doesn't provide the correct info, an email to Coronado or a review of the model railroad magazine index might help you more.
You might want to track down information specific to Carter Brothers. The Society for the Preservation of Carter Railroad Resources is a good place to check out. As always, trying to build an accurate model helps to bring out the rich history of the real thing.
Here's a page on SPCRR build a new truck for SP #472.
[
www.spcrr.org]
Michael