First, see...
86 K10 lighting issuesIf you still have a problem...
The '85 front side marker lamps
do 'blink' with the turn/hazard lights, as do the '91 front side markers. The light and dark blue wires of the front side marker lamps should connect to the light and dark blue wires of the left & right front turn signal lamp circuits, respectively. The brown wires of the front side marker lamps should connect to the brown wires of the front park lamps circuit. The front side markers DO NOT ground directly to body sheet metal. Rather, they ground through the filaments of their "paired" left and right front park/turn lamps, respectively. Check to see if the side marker lamps were grounded directly to the fender or radiator support sheet metal and correct the wiring, accordingly.
FYI - Filament type bulbs are indifferent to the direction (polarity) of the current flowing through their filaments. They illuminate similarly whether the filament is connected +- or -+. If the front side markers are populated with polarized LED bulbs (current flows in only one direction), the lamps will not function correctly because current flow through the side marker filaments reverses polarity depending on the logic state of the connected wiring. In other words, switched battery power supplies either or both leads of each side marker lamp depending on whether the running lamps and/or turn/hazard lamps are energized. The blue or brown side marker lamp lead NOT connected to a powered circuit finds ground through the unpowered park or turn filament of its 'paired' lamp. The reason this works without imparting a glow to the 'paired' lamp is because the electrical resistance of a 194 side marker lamp filament is much greater (the current threshold is much lower) than the resistance (current threshold) of its paired 1157 park/turn lamp filaments. That is to say, the current needed to illuminate a 194 filament is negligible compared to the current needed to illuminate the 1157 filaments. So the 194 bulb can ground through the filaments of the 1157 bulb without illuminating the 1157 bulb.
Did this make sense or did I leave you confused?