J55 Brake System Question

[84C10EC]

I'm needing to replace some brake components on my 1984 Chevy C10 Silverado. My GM service parts sticker indicates that the the truck has a J55 BRAKE SYSTEM, HEAVY DUTY. None of my local parts stores or even my local Chevy parts center can differentiate this code into anything meaningful. The closest code they can find based on my truck make and model is JB5. My VIN brake code is E which indicates a 6000-7000 lbs system. JB5 does correspond with a BRAKE, POWER, DISC/DRUM, 6400 LBS which seems to match. Does the J55 brake system correspond with JB5 parts? Can anyone confirm this? Thanks!