According to wiring diagrams for that era of 4/4 there were two changeover relays in the dash area associated with selection of the hazard warning lights, possibly the ones taped together. This as well as a flasher relay which appears on first glance to service direction indicators and hazards.
Regarding LED replacements for indicators suggest discussing this with Duncan at Classic Car LED's. One option may be using his CANBUS friendly LED's which draw enough current to simulate filament bulbs, another would fitting his LED flasher relay, final and most laborious would be fitting resistors across each of the four indicators.
