The arguments for parallel or series install of the resistor litter the interwebs. For the GRiSO, the dash doesn't care. It just wants to see a load. Since the front and rear indicators share a common ground at each end, I would just stick one resistor in series in the grounds at each end, then laugh maniacally.
Use 20W wire-wound resistors.
--- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---
..[You must be registered and logged in to see this image.].In GRiSO we trust!
.