why do yo need to know ? what year truck you have ? 84-up is not same as 83 down, and in 77 or 78 things changed too on the columns, minor things, other than the steering wheel and cap, appearance mainly,
if you have an 84-up then you can use 88-91 k5 and 1 ton trucks columns too
van columns can work but you gotta shorten the shaft after the firewall part of it, 80-up are keyswitch type column, 79 older key on dash still
i have an 82 column i can measure if you really need to know for some odd reason, you need to know entirelength with the intermediate shaft and all, or just length of the column itself ?
from top end of shaft down to where ?
and why?
good luck