Scored Deal on CPP Disc Brake Kit & Question: 47-54 vs 55-59 Rear Leaf Question

[Dan in Pasadena]

I found a local guy thru CL w/ NIB parts for 47-54 AD trucks he is selling cheap. Fortunately, the disc brake conversion kit for those is the same as for 55-59's so I picked it up from him still in boxes for my '55 for just $275! I THINK that's a great price, huh? This is the kit w/ caliper brackets, calipers, pads, rotors, bearings & seals, dust caps, rubber brake lines. Plain disc, not drilled/slotted. No master cylinder but I still think I did well.

QUESTION: Same guy has a rear leaf spring kit for lowering 3" complete with shocks, spring perches, shock mounts, U bolts, etc for the 47-54 trucks. CPP website makes it LOOK like the same parts as for the 55-59 trucks but two different kits are listed. Anyone know if they're the same, nealy the same (what's the diff?) or totally different and won't work in my later truck? Any advice appreciated, Dan