Every time I do one of these I use the Haynes manual I have had for YEARS. I have never had a problem swapping them out or problems with the schematics.
They Haynes shows full schematics for the dummy light setup, but has a separate part for the specific pins on the cluster. Being 84 vs 85, there shouldn't be much difference especially if both are in operational order. The last time I put an 86 full guage C10 cluster in a 81 2WD K5 dummy light in about 30 minutes using these schematics.
If you don't like the one in there, I would suggest purchasing a Helm's owners manual.