According to the 1966 profile, it is 90# from Pueblo to LaVeta, dating from the early 1950's. There is a short 5 mile stretch that was upgraded in 1957 to 110# and 112#. It is 90# for the first five miles out of La Veta, then 110# to just above Sierra, then 90# until the last 9 miles out of Alamosa, where it is 85#. There is a tiny bit of 100# right at the sumit at Fir. The 110# rail dates from the late 1940's, the 90# rail dates from 1930 to 1940. The 85# is CF&I rail from 1909. I'm sure Earl can tell us if and where the line has been upgraded.
Michael Allen