There are some subtle differences in parts for the various years.
The 48-50 have the set-up indicated in the drawing shown by Tim. They also bolt through the locking tang as shown. I have posted pictures of later versions which have a 1/2 twist and a pin/cotter in that location. The other difference is the small bracket for the rod on the dash right behind the knob 48 and 54 are held with two bolts other years with just one. When they used the straight rod they also increased the length of the bracket I have posted pictures so you can see:
Short bracket 1949-50
http://good-times.webshots.com/photo/2170202530102454676vCrOsX
Long bracket 1951-53
http://good-times.webshots.com/photo/2954501030102454676TjkaDl
Unique 1948 bracket
http://good-times.webshots.com/photo/2769735300102454676UudoGQ
Unique 1954 bracket (not sure on 55 1st)
http://good-times.webshots.com/photo/2819720760102454676CuQDBk
1950 version (straightened rod by po)with Z-bar
http://good-times.webshots.com/photo/2602080550102454676drEvVn

1950 Chevrolet 3/4-Ton 3600
More pictures on Flickr