where is dashboard ground wire on 1987 olds custom cruiser?

believe there is not a wire...the dash assembly is grounded...you will notice that the cigarette lighter has but one wire goin' to it?...that's because the receptacle is grounded by the steel dashboard in that location~ there could be a wire~ self-tapping screw into in inconspicuous place under the dash....a "lolipop" wire lead and any length wire chosen is up to you~ the battery is grounded to frame with this 0 gauge (1/0) battery cable---clean the ends...connection to the chassis/ground for reliable power~

87 is going to be filthy with corrosion...the battery should be newer than five years old...the knock-off labels on the top of the battery will tell of it's age...the reason, your alternator has a variable output (givin' what's required of it) and if what is required is all that it can produce...the darned thing will burn out....because the battery was weak and old~ assure both battery terminals are clean (with a garden hose, NOT bakingsoda) to assure that 300 cold cranking amps can get through~