Up to 1980 all trucks with manual locking hubs were Spicers and 1981 on up were a regular version of Warns locking hub ( without the Warn sticker on them ) -- Note : this is only true for those trucks that came with manual locking hubs , the full time and auto locking stuff had there own styles.
As far as I know a locking hub was always offered as an option on a solid axle 69 to 91 truck.
Tom
There is one exception that I can think of - A 1981 K-30 still offered a Spicer Hub and than in 1982 they went with the Warn style.