Here is some info on the different brake valves and what they do as well as how to rebuild them and where to obtain parts:
https://www.youtube.com/watch?v=VdlfzcWCekshttps://www.youtube.com/watch?v=qzUk8W1-2pwhttps://www.youtube.com/watch?v=9kOCpaFGWGwhttps://www.youtube.com/watch?v=33vnQG6p9I4
Whitey: 1996 F 250 XL CCLB 4X4 7.3 DI ZF5 (The Work Horse) Lots of power mods
Whitey Jr: AKA Jr 1982 F 150 CCLB 4X4 351W C6 (Jr Work Horse) respectable power, but not over the top
The Bronco: 1987 Bronco XLT 351W C6 (needs work) Lots of off road mods and plenty of power mods
The Dodge: 2006 Ram 2500 CCSB 4X4 5.9 HO Cummins (The reliable ride that cant keep an AC in itself) (5th AC go around almost complete)