Rebuilt 1926

A question since my knowledge of D&RGW history is a bit vague:
The wood revenue freight cars seem to all be labeled "Rebuilt 1926"

Why were they rebuilt?

I have been told that the FRA rules were changing and new cars had to have steel frames so the D&RGW rebuilt the wood frame cars to squeeze more life out of them.
Is this reasonably accurate?

Were the cars also converted to a K-1 - C (Reservoir directly attached to the Cylinder) system at the same time?
The K-1-D system has a hose between the Reservoir and cylinder which can be problematic

All of the above would explain why several of the non-revenue cars have a K-1-D brake system AND why the K-1-C system is often a VERY tight fit on the revenue cars.

The C&TS does have one boxcar with K-1-D. I have been told it was missed during the 1926 rebuild.

This comes up a lot from my crew during work sessions and I don't want to be spreading lies!
(I make up enough "facts" as it is....)

Thanks in advance for any insight!
Clyde "deerslayer" Putman
Dallas, TX, USA