Actually, '50 was the last year for Huck brakes and '49 was the last year of knee action shocks. If you are looking to order pre-fabbed brakelines, you have some decisions to make on what brakes you are going to run.
There are differences between the size of the tubing and how they were routed. For example, I know that the '50 (Huck) used mostly 3/8" lines and a single line that comes out off of the master cylinder. This single line goes to the passenger side frame rail. The front left wheel is fed from a line that T's off of the front right wheel and runs across the crossmember under the radiator. Later years T'ed out the back of the master and ran a 1/4" line to the front left wheel along the left frame rail. This is why you see a different number of lines listed in the catalogs. I believe that the later bendix brakes used 1/4" lines, but I also think that this doesn't hold true for all years. The Huck and Bendix Master cylinders also have a different bore.
I believe, but do not know for sure, that you can just pick a year for your brake system and put it in any AD frame. Most folks prefer the later Bendix system unless you are doing a total stock restore. Also look at the cost of replacement parts, (cylinders, shoes, etc.) and you will see a wide variance. Some parts are one year only.
I have a '50 truck, with '50 3/8 lines, a 54 master, '51 front bendix, (needed an 3/8 to 1/4 reducers at front rubber lines) and '59 rear Bendix. With the '59 rear axle, I had to get a longer than stock '50 rubber rear line to go from the frame to the axle. I don't rembember what year the rubber line was but it was one year only and it was pricy. The system works fine. If I had to do it over, I might go with the later style brake lines.
Finally, doesn't the '54, 55-1 frame have less of rear axle hump? (i.e. flatter than earlier frames)
